SN7
SHORT NOTE
5M
Describe the 22q11.2 Deletion of DiGeorge Syndrome.
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.
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.
Hypocalcaemic seizures with cardiac defect suggest the diagnosis.
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