Pediatrics
Final Professional MBBS — Pediatrics. Complete question bank: Long Questions (10 marks) and Short Notes (5 marks) across all 15 systems, with clinical pearls, drug doses, staging tables, mnemonics and key-point recaps.
DEFINITION
Down syndrome is the commonest chromosomal disorder and the commonest genetic cause of intellectual disability, resulting from an extra copy of chromosome 21 (trisomy 21).
CYTOGENETIC TYPES
Type Frequency Note Free trisomy 21 (non-disjunction) ~95% 47,XX/XY,+21; linked to advanced maternal age Translocation (Robertsonian, e.g. 14;21) ~4% May be inherited; NOT age-related; higher recurrence risk Mosaicism ~1% Two cell lines; often a milder phenotype CLINICAL FEATURES
- Craniofacial — brachycephaly with a flat occiput, upslanting palpebral fissures, epicanthic folds, Brushfield spots (iris), flat nasal bridge, small ears, and a protruding tongue.
- Hands/feet — a single transverse palmar (simian) crease, clinodactyly of the 5th finger, and a wide 'sandal gap' between the 1st and 2nd toes.
- Generalised hypotonia, short stature and intellectual disability.
ASSOCIATED ANOMALIES (must be actively screened for)
- Congenital heart disease — atrioventricular (endocardial cushion) defect is characteristic; also VSD.
- Gastrointestinal — duodenal atresia (double-bubble), Hirschsprung disease.
- Hypothyroidism, atlantoaxial instability, an increased risk of leukaemia (ALL/AML), hearing and visual defects, obstructive sleep apnoea, and early Alzheimer changes.
DIAGNOSIS
- Clinical suspicion confirmed by karyotype (also identifies the type — essential for recurrence-risk counselling).
- Antenatal screening — combined first-trimester test (nuchal translucency + PAPP-A + β-hCG), maternal serum markers, and NIPT (cell-free fetal DNA); confirmed by CVS/amniocentesis.
MANAGEMENT
- Multidisciplinary care — treat associated conditions (cardiac surgery, thyroid, etc.).
- Early intervention/therapy (physiotherapy, speech, special education) to optimise development.
- Routine health surveillance — thyroid, hearing, vision, cardiac and (as indicated) atlantoaxial screening.
- Family support and genetic counselling (recurrence risk depends on the cytogenetic type).
EPIDEMIOLOGY & RISK
- The commonest autosomal trisomy compatible with survival; incidence rises with maternal age.
- Recurrence risk is low for non-disjunction but higher for the inherited translocation form.
DEVELOPMENT & COGNITION
- Global developmental delay with mild-to-moderate intellectual disability; language is often more affected than social skills.
- Early intervention improves functional outcomes; many achieve semi-independent living.
HEALTH-SURVEILLANCE SCHEDULE
- Birth — echocardiogram, red-reflex, hearing screen, thyroid function.
- Ongoing — periodic thyroid, vision and hearing checks; growth on Down-specific charts; atlantoaxial assessment before sports.
DIFFERENTIAL DIAGNOSIS
- Other trisomies and syndromes with hypotonia and facial anomalies; congenital hypothyroidism (also hypotonia, macroglossia).
- Karyotype settles the diagnosis.
PROGNOSIS
Life expectancy has improved greatly (into adulthood) with treatment of heart defects and infections; the main determinants are cardiac disease and, later, early-onset Alzheimer disease.
MECHANISM OF NON-DISJUNCTION
Most cases arise from meiotic non-disjunction (failure of chromosome-21 pairs to separate), usually in maternal meiosis — the basis of the maternal-age effect. Translocation cases involve fusion of chromosome 21 with another acrocentric chromosome (commonly 14).
GROWTH & FEEDING
- Short stature and feeding difficulties (hypotonia) are common in infancy; plot growth on Down-specific charts.
- Obesity, constipation and dental problems need attention in later childhood.
ANTENATAL SCREENING IN DETAIL
- First-trimester combined test — increased nuchal translucency, low PAPP-A, raised free β-hCG.
- Second-trimester quadruple marker and, increasingly, NIPT; ultrasound soft markers support risk assessment.
- A high-risk screen is confirmed by CVS/amniocentesis karyotype.
FAMILY SUPPORT
Parents benefit from early, balanced counselling, contact with support groups, and a clear surveillance plan; emphasising the child's potential and needs (not just the diagnosis) is important.
📝CLINICAL / APPLIED POINTS- Confirm with a karyotype — it distinguishes non-disjunction from a translocation, which changes recurrence risk.
- Every newborn with Down syndrome needs an echocardiogram (AV canal defect is easily missed clinically).
- Screen lifelong for hypothyroidism, hearing/vision problems and, before sports, atlantoaxial instability.
- Translocation Down syndrome may be inherited — test the parents for a balanced translocation.
- Focus on function and inclusion — many individuals lead fulfilling, semi-independent lives.
🔑KEY POINTS TO REMEMBER- Commonest chromosomal disorder; trisomy 21 (95% non-disjunction, 4% translocation, 1% mosaic).
- Upslanting fissures, epicanthic folds, Brushfield spots, simian crease, sandal gap, hypotonia.
- Associations: AV canal defect, duodenal atresia, hypothyroidism, leukaemia, atlantoaxial instability.
- Confirm by karyotype (types the disorder for counselling); antenatal screen/NIPT.
- Multidisciplinary care + surveillance + early intervention + genetic counselling.
📚SOURCES: Ghai Essential Pediatrics; Nelson Textbook of Pediatrics.DEFINITION
Turner syndrome is a disorder of females caused by complete or partial absence of one X chromosome (classically 45,X monosomy), resulting in gonadal dysgenesis and short stature.
CYTOGENETICS
- 45,X (monosomy X) in about half; the rest are mosaics (45,X/46,XX) or have X structural abnormalities (isochromosome, deletions).
- Not associated with advanced maternal age.
CLINICAL FEATURES
- Short stature — the most consistent feature.
- Neonatal — lymphoedema of the hands and feet and redundant neck skin.
- Webbed neck, low posterior hairline, shield chest with widely spaced nipples, cubitus valgus, short 4th metacarpal, multiple pigmented naevi, high-arched palate.
- Gonadal dysgenesis ('streak ovaries') → delayed/absent puberty, primary amenorrhoea and infertility.
- Usually normal intelligence.
ASSOCIATED ANOMALIES
- Cardiac — coarctation of the aorta and bicuspid aortic valve.
- Renal — horseshoe kidney; recurrent otitis media and hearing loss; autoimmune thyroiditis.
DIAGNOSIS
- Karyotype (45,X or variant) is confirmatory; FISH for mosaicism.
- Hypergonadotropic hypogonadism — raised FSH and LH with low oestrogen.
- Echocardiography and renal ultrasound for associated anomalies.
MANAGEMENT
- Growth hormone to improve final height.
- Oestrogen replacement to induce puberty and maintain secondary sexual characteristics/bone health.
- Management of cardiac and renal anomalies; hearing and thyroid surveillance.
- Fertility counselling (assisted reproduction/oocyte donation) and psychological support.
GROWTH & PUBERTY
- Short stature is present from childhood; specific Turner growth charts are used.
- Most have ovarian failure needing induced puberty; a minority (mosaics) may menstruate/rarely conceive.
IMPORTANCE OF THE KARYOTYPE (Y material)
Detecting Y-chromosome material (in some mosaics) is important because it raises the risk of gonadoblastoma, for which gonadectomy is considered.
PSYCHOSOCIAL & PROGNOSIS
Intelligence is usually normal, though specific visuospatial/social difficulties occur; with growth hormone, oestrogen therapy and management of cardiac/renal issues, most women lead healthy, productive lives.
DIFFERENTIAL DIAGNOSIS
- Other causes of short stature (GH deficiency, hypothyroidism, skeletal dysplasia) and of primary amenorrhoea.
- Noonan syndrome ('male Turner-like' phenotype but normal karyotype, autosomal dominant, pulmonary stenosis).
MONITORING
- Regular cardiac (aortic dimensions), renal, thyroid, hearing and bone-density review.
- Growth on Turner-specific charts; monitor response to growth hormone/oestrogen.
NEONATAL PRESENTATION
- Congenital lymphoedema of the dorsa of hands and feet and loose nuchal skin folds are early neonatal clues.
- A neonate with lymphoedema, a heart murmur (coarctation) or webbed neck warrants a karyotype.
GROWTH-PROMOTING & PUBERTAL THERAPY
- Growth hormone is started in early childhood to improve final adult height.
- Oestrogen (then oestrogen-progesterone) is introduced at the appropriate age to induce puberty, complete growth and protect bone.
TRANSITION & ADULT ISSUES
- Lifelong follow-up for the aorta (dilatation/dissection risk, especially in pregnancy), hypertension, diabetes, thyroid and hearing.
- Structured transition to adult services with attention to fertility, bone and cardiovascular health.
FERTILITY & PREGNANCY
- Most women are infertile (streak gonads); pregnancy is possible via oocyte donation/assisted reproduction.
- Pregnancy carries a real risk of aortic dissection — cardiac assessment and monitoring are essential beforehand.
KEY EXAM POINT
Turner is the classic cause of short stature with delayed puberty in a phenotypic girl — a karyotype is mandatory, and growth hormone plus timed oestrogen therapy address height and puberty while cardiac/renal anomalies are managed.
ASSOCIATED AUTOIMMUNE & METABOLIC ISSUES
- Higher rates of autoimmune thyroiditis, coeliac disease, type 2 diabetes and hypertension.
- Screen periodically and manage proactively as part of lifelong care.
📝CLINICAL / APPLIED POINTS- Think Turner in any girl with unexplained short stature or delayed puberty — check a karyotype.
- Neonatal lymphoedema of hands/feet with neck webbing is an early clue.
- Always evaluate the heart (coarctation, bicuspid valve) and kidneys.
- Raised FSH/LH with low oestrogen confirms primary ovarian failure.
- Growth hormone plus timely oestrogen replacement addresses the two main issues (height and puberty).
🔑KEY POINTS TO REMEMBER- 45,X (or variant) in females → gonadal dysgenesis + short stature.
- Short stature, webbed neck, shield chest, cubitus valgus, streak ovaries; neonatal lymphoedema.
- Associations: coarctation/bicuspid aortic valve, horseshoe kidney; usually normal IQ.
- Karyotype + high FSH/LH (hypergonadotropic hypogonadism).
- Growth hormone + oestrogen replacement + manage cardiac/renal + fertility counselling.
📚SOURCES: Ghai Essential Pediatrics; Nelson Textbook of Pediatrics.INTRODUCTION
Genetic disorders are inherited in Mendelian (single-gene) and non-Mendelian patterns. Recognising the pattern from the pedigree allows diagnosis, recurrence-risk estimation and counselling.
AUTOSOMAL DOMINANT (AD)
- Vertical transmission — affected individuals in every generation; males and females equally affected.
- An affected parent has a 50% risk in each child; features include variable expression and incomplete penetrance.
- Examples — achondroplasia, Marfan syndrome, neurofibromatosis, Huntington disease.
AUTOSOMAL RECESSIVE (AR)
- Horizontal pattern — usually affected siblings with unaffected (carrier) parents; associated with consanguinity.
- Two carrier parents have a 25% risk per child.
- Examples — thalassaemia, cystic fibrosis, sickle cell disease, most inborn errors of metabolism, PKU.
X-LINKED RECESSIVE
- Males affected, females are carriers; no male-to-male transmission.
- A carrier mother transmits to 50% of sons (affected) and 50% of daughters (carriers).
- Examples — haemophilia, Duchenne muscular dystrophy, G6PD deficiency, red-green colour blindness.
X-LINKED DOMINANT
- Affected males and females; no male-to-male transmission; may be lethal in males.
- Examples — Rett syndrome, X-linked (vitamin D-resistant) hypophosphataemic rickets.
NON-MENDELIAN INHERITANCE
Pattern Feature / example Mitochondrial Maternal inheritance (all children of affected mother); MELAS, Leber optic neuropathy Genomic imprinting Expression depends on parent of origin; Prader-Willi/Angelman Multifactorial/polygenic Genes + environment; neural-tube defects, cleft lip/palate, most CHD Trinucleotide repeat (anticipation) Earlier/more severe in successive generations; Fragile X, Huntington KEY CONCEPTS / TERMINOLOGY
Term Meaning Penetrance Proportion of gene-carriers who show the trait Expressivity Severity/variability of expression among affected Anticipation Earlier/more severe in successive generations Mosaicism Two genetically different cell lines in one person New mutation No family history (e.g. many achondroplasia cases) PEDIGREE ANALYSIS
- Squares = males, circles = females; a horizontal line = mating; shaded = affected.
- A three-generation pedigree with consanguinity loops and affected relatives reveals the pattern.
WHY PATTERN MATTERS
Identifying the inheritance pattern gives the recurrence risk and guides carrier testing, prenatal diagnosis and counselling for the family.
CONSANGUINITY & COMMUNITY
Consanguineous marriage increases the risk of autosomal recessive disorders (both partners more likely to carry the same rare allele); this is relevant in many Indian communities and informs premarital counselling.
REPRESENTATIVE DISORDERS
Pattern Examples AD Achondroplasia, Marfan, NF1, Huntington AR Thalassaemia, CF, sickle cell, PKU, Wilson X-linked recessive Haemophilia, DMD, G6PD, colour blindness Mitochondrial MELAS, Leber optic neuropathy SEX-LIMITED & SEX-INFLUENCED TRAITS
- Sex-limited — expressed in one sex only (e.g. features confined to one sex despite autosomal inheritance).
- Sex-influenced — expressed differently in the two sexes (e.g. pattern baldness).
MOSAICISM & NEW MUTATIONS
A new (de novo) mutation explains an affected child with no family history (common in achondroplasia); germline mosaicism in a parent can cause recurrence despite apparently unaffected parents — an important counselling point.
APPLICATION TO COUNSELLING
- The pattern gives the numerical recurrence risk quoted to families (AR 25%, AD 50%, X-linked risks by sex).
- It also identifies at-risk relatives who may benefit from carrier testing and reproductive counselling.
KEY EXAM POINT
A quick pedigree usually settles the mode of inheritance: consanguinity + affected sibs = AR; every generation affected = AD; only males affected with carrier mothers = X-linked recessive; all children of an affected mother = mitochondrial.
📝CLINICAL / APPLIED POINTS- Draw a three-generation pedigree — the pattern usually reveals the mode of inheritance.
- Consanguinity and affected siblings with normal parents suggest autosomal recessive.
- No male-to-male transmission with only affected males suggests X-linked recessive.
- All children of an affected mother (but none of an affected father) affected → mitochondrial.
- Worsening severity down the generations (anticipation) suggests a triplet-repeat disorder.
🔑KEY POINTS TO REMEMBER- AD: vertical, 50% risk, variable expression (achondroplasia, Marfan, NF).
- AR: horizontal, consanguinity, 25% risk (thalassaemia, CF, sickle, IEM).
- X-linked recessive: males affected, no male-male transmission (haemophilia, DMD, G6PD).
- Mitochondrial = maternal; imprinting = parent-of-origin (Prader-Willi/Angelman).
- Anticipation (triplet repeats) — Fragile X, Huntington; multifactorial — NTD, cleft, CHD.
📚SOURCES: Ghai Essential Pediatrics; Nelson Textbook of Pediatrics.DEFINITION
A dysmorphic child has abnormal physical features arising from abnormal development. A systematic approach helps reach a specific diagnosis, which guides management, prognosis and recurrence-risk counselling.
KEY TERMINOLOGY
Term Meaning Malformation Intrinsic abnormal development (e.g. cleft lip) Deformation Abnormal mechanical force on normal tissue (e.g. club foot from oligohydramnios) Disruption Breakdown of normal tissue (e.g. amniotic bands) Dysplasia Abnormal tissue organisation (e.g. skeletal dysplasia) Sequence One anomaly triggers a cascade (e.g. Potter sequence) Syndrome Recognised pattern from a single cause HISTORY
- Antenatal — teratogen/drug/alcohol exposure, maternal illness (diabetes), infections (TORCH), oligo/polyhydramnios.
- Family history — a three-generation pedigree, consanguinity, recurrent miscarriages, similarly affected relatives.
- Birth and developmental history.
EXAMINATION
- Growth parameters including head circumference; note proportionate vs disproportionate.
- Systematic head-to-toe survey for major and minor anomalies (facies, ears, eyes, hands, genitalia), with objective measurements (inter-canthal distance, span, etc.).
- Examine parents/relatives where relevant.
INVESTIGATIONS
- Karyotype for suspected chromosomal disorders; FISH for microdeletions (e.g. 22q11).
- Chromosomal microarray (copy-number changes) and targeted molecular/gene testing.
- Metabolic screen (TMS/urine organic acids) if an IEM is suspected; imaging (skeletal survey, echo, cranial/renal ultrasound).
APPROACH & MANAGEMENT
- Pattern recognition (and use of dysmorphology databases) to reach a syndromic diagnosis.
- Multidisciplinary management of the associated problems; developmental support.
- Genetic counselling — diagnosis, prognosis, recurrence risk and options.
MINOR vs MAJOR ANOMALIES
- Minor anomalies (e.g. single palmar crease, epicanthic folds, ear tags) have little functional impact but, when multiple, flag an underlying syndrome.
- Major anomalies (e.g. congenital heart disease, cleft palate, neural-tube defect) have functional/cosmetic consequences and need treatment.
COMMON PATTERNS TO RECOGNISE
- Down (upslanting fissures, simian crease), Turner (webbed neck, short stature), Marfan (tall, arachnodactyly).
- DiGeorge (cardiac + hypocalcaemia), Prader-Willi (hypotonia → obesity), fetal alcohol syndrome (teratogen).
MULTIDISCIPLINARY CARE
Once a diagnosis is reached, a team (paediatrics, cardiology, surgery, ophthalmology, genetics, therapy services) manages the associated problems, and the family receives counselling and support.
COMMON TERATOGENS (a key history point)
- Alcohol (fetal alcohol syndrome), phenytoin, valproate, warfarin, retinoids, thalidomide.
- Maternal diabetes, and congenital infections (TORCH) — rubella, CMV, toxoplasma.
WHEN TO REFER TO GENETICS
- Multiple anomalies, dysmorphism with developmental delay, a positive family history, or diagnostic uncertainty.
- Before/after prenatal testing and for recurrence-risk counselling.
DEFORMATION vs MALFORMATION (clinical value)
Distinguishing a deformation (e.g. positional talipes from oligohydramnios — good prognosis, often correctable) from a malformation (intrinsic, e.g. a structural heart defect) matters for prognosis, recurrence risk and management.
PROGNOSIS & COUNSELLING
Prognosis depends entirely on the specific diagnosis and its associated anomalies; even without a treatment change, a precise diagnosis provides the family with recurrence risk, expected complications to watch for, and access to support networks.
PRINCIPLES OF EVALUATION (summary)
Detailed history (antenatal, family, pedigree) → Systematic examination with measurements → Targeted investigations (karyotype/microarray/molecular/metabolic/imaging) → Pattern recognition → diagnosis → Multidisciplinary management + genetic counselling
KEY EXAM POINT
Multiple minor anomalies together are a red flag for an underlying syndrome; chromosomal microarray is the recommended first-line test for unexplained dysmorphism with developmental delay.
📝CLINICAL / APPLIED POINTS- A careful history (teratogens, consanguinity) and pedigree are as important as the examination.
- Distinguish malformation from deformation/disruption — it changes cause, recurrence and prognosis.
- Objective measurements turn a vague 'odd-looking' impression into definable anomalies.
- Chromosomal microarray is now a key first-line test for unexplained dysmorphism/developmental delay.
- A precise diagnosis matters for counselling even when it doesn't change day-to-day treatment.
🔑KEY POINTS TO REMEMBER- Dysmorphism = abnormal features from abnormal development; aim for a specific diagnosis.
- Know terms: malformation, deformation, disruption, dysplasia, sequence, syndrome.
- History (teratogens, consanguinity, pedigree) + systematic exam with measurements.
- Karyotype/FISH/microarray + molecular + metabolic + imaging as indicated.
- Pattern recognition → multidisciplinary care + genetic counselling.
📚SOURCES: Ghai Essential Pediatrics; Nelson Textbook of Pediatrics.DEFINITION
Genetic counselling is a communication process that helps a family understand a genetic condition — its diagnosis, natural history, recurrence risk and available options. It is non-directive, voluntary and confidential.
INDICATIONS
- A previous affected child or a family history of a genetic disorder.
- Consanguinity; advanced maternal age; recurrent pregnancy loss.
- An abnormal antenatal screening test or ultrasound; known carrier status (e.g. thalassaemia).
STEPS IN COUNSELLING
Establish an accurate diagnosis → Construct a pedigree → Estimate the recurrence risk (by inheritance pattern) → Communicate risks/options non-directively → Provide ongoing support
RECURRENCE RISK (examples)
- Autosomal recessive — 25% for two carrier parents.
- Autosomal dominant — 50% if a parent is affected.
- Chromosomal — depends on the type (e.g. translocation Down syndrome differs from non-disjunction).
PRENATAL SCREENING vs DIAGNOSIS
Category Tests Screening (risk estimation) Maternal serum markers (double/triple/quadruple), first-trimester combined test (NT + PAPP-A + β-hCG), NIPT (cell-free fetal DNA), anomaly ultrasound Diagnostic (definitive) Chorionic villus sampling (11–14 wk), amniocentesis (15–18 wk), cordocentesis — for karyotype/microarray/molecular tests PREVENTIVE OPTIONS
- Carrier screening and premarital/pre-pregnancy counselling (e.g. thalassaemia).
- Prenatal diagnosis with informed reproductive choice; preimplantation genetic diagnosis in selected families.
- Folic acid to prevent neural-tube defects; avoidance of teratogens.
ETHICAL PRINCIPLES
- Autonomy (the family decides), confidentiality, informed consent and a non-directive stance.
- Sensitivity around reproductive choices and disclosure within families.
TIMING OF PRENATAL TESTS
Test Timing First-trimester combined screen 11–14 weeks Chorionic villus sampling 11–14 weeks Amniocentesis 15–18 weeks Anomaly ultrasound 18–20 weeks PREVENTION AT COMMUNITY LEVEL
- Thalassaemia carrier screening and premarital counselling programmes (important in India).
- Periconceptional folic acid; rubella immunisation of girls; avoidance of teratogens/consanguinity awareness.
NIPT — STRENGTHS & LIMITS
- Non-invasive prenatal testing (cell-free fetal DNA) screens for common trisomies (21, 18, 13) with high sensitivity from ~10 weeks.
- It is a screening test — a positive result must be confirmed by a diagnostic test (CVS/amniocentesis).
SUPPORT & FOLLOW-UP
Counselling continues after results — supporting the family through decisions, arranging specialist input for an affected pregnancy/child, and planning care and future reproductive options.
PREIMPLANTATION GENETIC DIAGNOSIS (PGD)
For couples at high risk of a specific single-gene or chromosomal disorder, PGD tests embryos created by IVF before implantation, allowing transfer of unaffected embryos — an option that avoids termination of an established pregnancy.
CARRIER-SCREENING PROGRAMMES (India)
- Thalassaemia carrier screening with premarital/antenatal counselling has reduced affected births in high-prevalence regions.
- Community education, and rubella immunisation of girls, are complementary preventive measures.
COMMON SCREENING RESULTS (interpretation)
- Down syndrome — low PAPP-A, high β-hCG, increased nuchal translucency; low AFP on the quadruple test.
- Neural-tube defects — raised maternal serum AFP and confirmatory ultrasound.
KEY EXAM POINT
Distinguish screening from diagnosis clearly for families: a screen (serum markers/NIPT/USG) gives a risk, whereas only a diagnostic test (CVS/amniocentesis) provides certainty — and counselling remains non-directive throughout.
ROLE IN PREVENTION OF GENETIC DISEASE
Together, carrier screening, genetic counselling, prenatal diagnosis and (where appropriate) PGD form a preventive framework that — with folic acid supplementation and teratogen avoidance — reduces the burden of serious genetic and congenital disorders in the community.
📝CLINICAL / APPLIED POINTS- Counselling is non-directive — provide accurate information and support the family's own decision.
- An accurate diagnosis is the foundation; recurrence risk flows from the inheritance pattern.
- Screening tests estimate risk; only diagnostic tests (CVS/amniocentesis) confirm.
- NIPT has improved non-invasive detection of common trisomies but abnormal results still need confirmation.
- Carrier screening (e.g. thalassaemia) plus counselling is a powerful preventive strategy in India.
🔑KEY POINTS TO REMEMBER- Genetic counselling: non-directive communication about diagnosis, recurrence risk and options.
- Indications: previous affected child, family history, consanguinity, advanced maternal age, abnormal screen.
- Recurrence risk: AR 25%, AD 50%, chromosomal depends on type.
- Screening (serum markers, combined test, NIPT, USG) vs diagnostic (CVS, amniocentesis).
- Prevention: carrier screening, prenatal diagnosis, PGD, folic acid, avoid teratogens.
📚SOURCES: Ghai Essential Pediatrics; Nelson Textbook of Pediatrics.DEFINITION
Klinefelter syndrome is the commonest sex-chromosome disorder in males, caused by an extra X chromosome (classically 47,XXY), resulting in primary testicular failure.
CLINICAL FEATURES
- Often normal in childhood; recognised at puberty/adolescence.
- Tall stature with long legs, small firm testes, and gynaecomastia.
- Hypogonadism (reduced testosterone), infertility (azoospermia), and learning/behavioural difficulties.
DIAGNOSIS & MANAGEMENT
- Karyotype (47,XXY); hypergonadotropic hypogonadism — low testosterone with high FSH/LH.
- Testosterone replacement from puberty (secondary sexual characteristics, bone health, wellbeing).
- Fertility counselling (sperm retrieval techniques); educational/psychological support.
PATHOPHYSIOLOGY & VARIANTS
The extra X (usually from meiotic non-disjunction) impairs testicular development, causing seminiferous tubule dysgenesis and Leydig-cell dysfunction; higher-grade variants (48,XXXY) are more severely affected.
KEY EXAM POINT
Suspect Klinefelter in a tall adolescent boy with small firm testes and gynaecomastia; a karyotype confirms 47,XXY, and testosterone replacement plus fertility counselling are the mainstays.
ASSOCIATED PROBLEMS
- Increased risk of osteoporosis, metabolic syndrome, autoimmune disease and (slightly) breast cancer.
- Speech/language and learning support is often helpful in childhood.
KEY EXAM POINT (recap)
47,XXY causes hypergonadotropic hypogonadism — tall boys with small firm testes, gynaecomastia and infertility; testosterone replacement improves virilisation, bone health and wellbeing but does not restore fertility.
MULTIDISCIPLINARY CARE
Care involves endocrinology (testosterone), fertility specialists, speech/educational support and psychological input; early recognition improves educational and social outcomes.
PROGNOSIS
With testosterone therapy and educational/psychological support, most individuals lead healthy, independent lives, though infertility usually persists.
🔑KEY POINTS TO REMEMBER- Commonest sex-chromosome disorder in males; 47,XXY.
- Tall stature, small firm testes, gynaecomastia, hypogonadism, infertility.
- Karyotype + high FSH/LH with low testosterone.
- Testosterone replacement + fertility counselling + educational support.
📚SOURCES: Ghai Essential Pediatrics; Nelson Textbook of Pediatrics.DEFINITION
Edward syndrome (trisomy 18) and Patau syndrome (trisomy 13) are severe autosomal trisomies with multiple malformations and a poor prognosis (most die in infancy).
EDWARD SYNDROME (Trisomy 18)
- Severe growth restriction, prominent occiput, micrognathia, low-set ears.
- Clenched hands with overlapping fingers, rocker-bottom feet.
- Congenital heart disease; poor prognosis.
PATAU SYNDROME (Trisomy 13)
- Midline defects — holoprosencephaly, cleft lip/palate, microphthalmia.
- Postaxial polydactyly, scalp defects (cutis aplasia), congenital heart disease.
- Poor prognosis.
DIAGNOSIS
Suspected clinically and on antenatal ultrasound; confirmed by karyotype. Management is largely supportive/palliative given the poor prognosis, with genetic counselling.
EPIDEMIOLOGY & PROGNOSIS
- Both are associated with advanced maternal age and are frequently detected on antenatal ultrasound.
- Most affected infants die in the first year; care is supportive/palliative, with honest counselling.
KEY EXAM POINT
Remember the hand/foot clues — overlapping clenched fingers and rocker-bottom feet in Edward (18), and polydactyly with midline/holoprosencephaly defects in Patau (13).
COUNSELLING & CARE
Given the poor prognosis, care is compassionate and largely palliative; parents need clear, sensitive counselling about the diagnosis, prognosis and options, plus recurrence-risk advice (usually low for non-disjunction trisomy).
CLINICAL COMPARISON
Feature Edward (18) Patau (13) Head/face Prominent occiput, micrognathia Microcephaly, cleft lip/palate Hands/feet Overlapping fingers, rocker-bottom feet Postaxial polydactyly CNS — Holoprosencephaly Prognosis Poor Poor KEY EXAM POINT
Both trisomies carry a poor prognosis with death usually in infancy; recognising the hand/foot and midline clues, confirming by karyotype, and providing compassionate palliative care and counselling are the priorities.
🔑KEY POINTS TO REMEMBER- Severe autosomal trisomies with poor prognosis (death usually in infancy).
- Edward (18): growth restriction, overlapping clenched fingers, rocker-bottom feet, CHD.
- Patau (13): holoprosencephaly, cleft lip/palate, polydactyly, scalp defects, CHD.
- Confirm by karyotype; supportive care + genetic counselling.
📚SOURCES: Ghai Essential Pediatrics; Nelson Textbook of Pediatrics.DEFINITION
Fragile X syndrome is the commonest inherited cause of intellectual disability. It is an X-linked disorder caused by a CGG trinucleotide-repeat expansion in the FMR1 gene, and shows anticipation (worsening in successive generations).
CLINICAL FEATURES
- Intellectual disability (more marked in males), autism-spectrum features and hyperactivity.
- Long face with a prominent jaw, large protruding ears, and (post-pubertal) macro-orchidism.
- Joint laxity; carrier females may be mildly affected.
DIAGNOSIS & MANAGEMENT
- Molecular testing for the CGG-repeat expansion (has replaced cytogenetic 'fragile site' testing).
- Supportive — special education, behavioural and speech therapy; genetic counselling.
GENETICS & ANTICIPATION
A normal-sized CGG repeat is stable, a 'premutation' can expand to a 'full mutation' when transmitted through the mother, silencing FMR1 — explaining anticipation and why the mother's carrier status matters.
KEY EXAM POINT
Consider Fragile X in any boy with intellectual disability and autistic features, especially with a long face, large ears and (after puberty) large testes; molecular repeat testing confirms it.
ASSOCIATED FEATURES & CARRIERS
- Connective-tissue signs (joint laxity, flat feet, mitral valve prolapse) and mood/anxiety problems.
- Female premutation carriers may develop premature ovarian insufficiency; both sexes may have late-onset tremor/ataxia (FXTAS).
INHERITANCE COUNSELLING
Because expansion typically occurs during maternal transmission, the recurrence risk and carrier testing of at-risk female relatives are important; molecular testing defines premutation vs full mutation and guides counselling.
MANAGEMENT & SUPPORT
There is no cure; management is supportive — special education, speech and behavioural therapy, and treatment of associated problems (seizures, ADHD) — together with genetic counselling for the family.
PROGNOSIS
Intellectual disability is usually lifelong, but early intervention and behavioural/educational support improve function and quality of life.
🔑KEY POINTS TO REMEMBER- Commonest inherited cause of intellectual disability; X-linked FMR1 CGG-repeat expansion; anticipation.
- Intellectual disability, autism/hyperactivity, long face, large ears, macro-orchidism.
- Diagnose by molecular (repeat) testing.
- Supportive therapy + genetic counselling.
📚SOURCES: Ghai Essential Pediatrics; Nelson Textbook of Pediatrics.DEFINITION
Marfan syndrome is an autosomal dominant connective-tissue disorder caused by mutations in the fibrillin-1 (FBN1) gene, affecting the skeleton, eyes and cardiovascular system.
CLINICAL FEATURES
- Skeletal — tall stature, arachnodactyly (long fingers), arm span > height, joint hypermobility, pectus deformity, scoliosis, high-arched palate.
- Ocular — ectopia lentis (upward lens dislocation), myopia.
- Cardiovascular (life-threatening) — aortic root dilatation → dissection/rupture, and mitral valve prolapse.
DIAGNOSIS & MANAGEMENT
- Clinical diagnosis using the Ghent criteria (major features + family history/genetics).
- Regular echocardiographic monitoring of the aorta; beta-blockers (± others) to slow aortic dilatation; prophylactic aortic surgery when indicated.
- Avoid strenuous/contact sports; ophthalmology follow-up; genetic counselling.
DIFFERENTIAL DIAGNOSIS
- Homocystinuria (also tall with lens dislocation — but DOWNward, plus thrombosis and intellectual disability).
- Other connective-tissue disorders (e.g. Loeys-Dietz, Ehlers-Danlos).
KEY EXAM POINT
The dangerous feature is the aorta — progressive aortic root dilatation risks dissection; lifelong echo surveillance, beta-blockers and activity restriction protect against this.
SYSTEMIC SURVEILLANCE
- Cardiology (echo of aortic root, mitral valve), ophthalmology (lens, retina), and orthopaedics (scoliosis).
- Multidisciplinary review through growth; genetic counselling (50% risk, autosomal dominant).
EMERGENCY AWARENESS
An acute severe chest/back pain in a person with Marfan may signal aortic dissection — a surgical emergency; families should know the warning symptoms and the importance of adhering to surveillance and activity advice.
PROGNOSIS
With aortic surveillance, beta-blockade, activity modification and timely surgery, life expectancy approaches normal; the outcome hinges on protecting the aorta.
🔑KEY POINTS TO REMEMBER- Autosomal dominant fibrillin-1 (FBN1) connective-tissue disorder.
- Tall, arachnodactyly, span > height, pectus/scoliosis; upward lens dislocation.
- Aortic root dilatation/dissection is the life-threatening feature; MVP.
- Ghent criteria; echo surveillance + beta-blockers; avoid strenuous sport.
📚SOURCES: Ghai Essential Pediatrics; Nelson Textbook of Pediatrics.DEFINITION
Achondroplasia is the commonest skeletal dysplasia causing disproportionate short stature. It is autosomal dominant (most cases are new mutations, linked to advanced paternal age) due to a FGFR3 gene mutation affecting endochondral bone growth.
CLINICAL FEATURES
- Rhizomelic (proximal) short limbs with a relatively normal trunk length.
- Large head with frontal bossing and a depressed nasal bridge; 'trident' hand.
- Lumbar lordosis, and normal intelligence.
COMPLICATIONS & MANAGEMENT
- Foramen magnum stenosis (risk of cord compression/apnoea), hydrocephalus, spinal stenosis, and obstructive sleep apnoea.
- Supportive/multidisciplinary care; monitor for neurological complications; genetic counselling (50% risk to offspring).
PATHOPHYSIOLOGY
An activating FGFR3 mutation inhibits chondrocyte proliferation at the growth plate, impairing endochondral ossification (long bones) while membranous ossification (skull vault) is relatively preserved — hence short limbs with a large head.
KEY EXAM POINT
Intelligence is normal in achondroplasia; the important early risk is foramen magnum stenosis (cord compression, central apnoea), so infants need neurological monitoring.
MANAGEMENT DETAIL
- Monitor head circumference and neurology in infancy; polysomnography if sleep apnoea suspected.
- Address spinal stenosis in later childhood/adulthood; psychosocial support; emerging targeted therapies.
GENETICS & COUNSELLING
Achondroplasia is autosomal dominant with a 50% risk to offspring; two affected parents risk a lethal homozygous form. Most cases are de novo mutations associated with advanced paternal age.
PROGNOSIS
With normal intelligence and appropriate management of complications (foramen magnum/spinal stenosis, sleep apnoea), individuals with achondroplasia have a near-normal life expectancy and can lead independent lives.
KEY EXAM POINT (recap)
Disproportionate short-limbed short stature with a large head and normal intelligence in an otherwise well child suggests achondroplasia; watch for foramen magnum stenosis in infancy.
🔑KEY POINTS TO REMEMBER- Commonest skeletal dysplasia; AD FGFR3 mutation (often new mutation, paternal age).
- Rhizomelic short limbs, large head with frontal bossing, trident hand, normal IQ.
- Complications: foramen magnum stenosis, hydrocephalus, spinal stenosis, OSA.
- Supportive care + surveillance + genetic counselling.
📚SOURCES: Ghai Essential Pediatrics; Nelson Textbook of Pediatrics.DEFINITION
Prader-Willi and Angelman syndromes both involve the 15q11–q13 region and classically illustrate genomic imprinting — the phenotype depends on the parent of origin of the missing/abnormal genetic material.
PRADER-WILLI SYNDROME (loss of PATERNAL 15q11–13)
- Neonatal hypotonia and poor feeding, then hyperphagia and obesity in childhood.
- Short stature, hypogonadism, small hands/feet, almond-shaped eyes, and intellectual disability/behavioural problems.
ANGELMAN SYNDROME (loss of MATERNAL 15q11–13)
- 'Happy puppet' — ataxic, jerky movements, inappropriate laughter.
- Severe intellectual disability, absent speech, seizures.
DIAGNOSIS
Confirmed by molecular tests (methylation studies, FISH/microarray) of the 15q11–13 region — the same region, different parent of origin, gives two very different syndromes.
MECHANISMS
The syndromes arise from deletion, uniparental disomy or imprinting defects of 15q11–13; because certain genes are expressed only from one parental copy, loss of the paternal copy causes Prader-Willi and loss of the maternal copy causes Angelman.
KEY EXAM POINT
A hypotonic, poorly-feeding infant who later becomes hyperphagic and obese = Prader-Willi; a child with ataxia, seizures, no speech and paroxysms of laughter = Angelman — same locus, opposite parent of origin.
MANAGEMENT
- Prader-Willi — strict dietary/environmental control of hyperphagia, growth hormone, hormone replacement, and behavioural support.
- Angelman — seizure control, communication aids, physiotherapy and family support.
DIAGNOSTIC APPROACH
Methylation-specific testing of 15q11–13 detects most cases of both syndromes; further tests (FISH, microarray, uniparental disomy studies) define the exact mechanism, which affects recurrence risk.
PROGNOSIS & FOLLOW-UP
Both are lifelong conditions requiring multidisciplinary follow-up; Prader-Willi care centres on preventing obesity-related complications, and Angelman care on seizures, communication and mobility.
🔑KEY POINTS TO REMEMBER- Both involve 15q11–13; classic examples of genomic imprinting (parent-of-origin effect).
- Prader-Willi (paternal loss): neonatal hypotonia → hyperphagia/obesity, hypogonadism.
- Angelman (maternal loss): 'happy puppet' — ataxia, laughter, severe ID, seizures, no speech.
- Confirm with methylation/FISH/microarray studies.
📚SOURCES: Ghai Essential Pediatrics; Nelson Textbook of Pediatrics.DEFINITION
DiGeorge syndrome is caused by a microdeletion of chromosome 22q11.2, producing a variable combination of cardiac, immune, endocrine and facial abnormalities due to abnormal development of the 3rd/4th pharyngeal pouches.
FEATURES — the 'CATCH-22' mnemonic
- C — Cardiac defects (conotruncal — tetralogy of Fallot, truncus arteriosus, interrupted aortic arch).
- A — Abnormal facies.
- T — Thymic hypoplasia/aplasia → T-cell immunodeficiency (recurrent infections).
- C — Cleft palate.
- H — Hypocalcaemia (hypoparathyroidism) — may present with neonatal seizures.
- 22 — deletion of chromosome 22q11.2.
DIAGNOSIS & MANAGEMENT
- FISH or chromosomal microarray for the 22q11.2 deletion.
- Manage the cardiac defect, correct hypocalcaemia, address immunodeficiency (infection precautions/immunology), and provide multidisciplinary care.
IMMUNOLOGY & CALCIUM
- Thymic hypoplasia impairs T-cell numbers/function → recurrent viral/fungal infections (avoid live vaccines/irradiate blood if severe).
- Hypoparathyroidism causes hypocalcaemia, which may present as neonatal seizures/tetany.
KEY EXAM POINT
Think 22q11 deletion in a neonate with a conotruncal heart defect plus hypocalcaemic seizures; FISH/microarray confirms it, and management targets the heart, calcium and immune deficiency.
SPECTRUM & PROGNOSIS
The phenotype is highly variable (from severe neonatal presentation to mild learning/speech problems with a subtle facial appearance); with cardiac surgery, calcium correction and infection management, many children do well, though developmental and psychiatric issues may emerge.
MANAGEMENT SUMMARY
- Correct hypocalcaemia (calcium ± vitamin D analogues), manage the cardiac defect, and take infection precautions for the immunodeficiency.
- Speech therapy for cleft/velopharyngeal issues; developmental and psychiatric surveillance; genetic counselling.
PROGNOSIS
Outcome depends on the severity of the cardiac defect and immunodeficiency; many children do well after cardiac repair and calcium correction, with ongoing developmental and psychiatric surveillance.
🔑KEY POINTS TO REMEMBER- 22q11.2 microdeletion (3rd/4th pharyngeal pouch maldevelopment).
- CATCH-22: Cardiac (conotruncal), Abnormal facies, Thymic hypoplasia (T-cell defect), Cleft palate, Hypocalcaemia.
- Diagnose by FISH/microarray for 22q11.2.
- Treat cardiac defect, hypocalcaemia and immunodeficiency; multidisciplinary care.
📚SOURCES: Ghai Essential Pediatrics; Nelson Textbook of Pediatrics.