Describe the vitamin B complex deficiency disorders.

Vitamin B Complex Deficiencies

• Thiamine (B1) deficiency causes beriberi, classically in populations eating polished (milled) rice, since the thiamine lies in the outer layers removed by polishing
• Wet beriberi — high-output cardiac failure with oedema, breathlessness and cardiomegaly
• Dry beriberi — peripheral neuropathy with wasting, paraesthesia and foot drop
• Infantile beriberi — in breastfed infants of thiamine-deficient mothers, presenting with aphonia (a characteristic hoarse, soundless cry), cardiac failure and convulsions; it can be rapidly fatal and responds dramatically to thiamine
• Wernicke encephalopathy and korsakoff psychosis occur in alcoholics, which is now the commonest setting in clinical practice
• The practical rule that follows — give thiamine before any glucose infusion in a malnourished or alcoholic patient, since a glucose load consumes the remaining thiamine and can precipitate Wernicke encephalopathy
• Prevention — parboiling of rice before milling, which drives thiamine into the grain and is the traditional protective practice; under-milling; avoiding washing rice repeatedly and discarding the cooking water; and eating whole grains and pulses
• Riboflavin (B2) deficiency — ariboflavinosis — is the commonest B vitamin deficiency in India, though rarely severe
• Its signs — angular stomatitis, cheilosis, glossitis with a magenta tongue, nasolabial seborrhoea and corneal vascularisation
• Niacin (B3) deficiency causes pellagra, remembered by the three (or four) Ds — dermatitis, diarrhoea, dementia and, untreated, death
• The dermatitis is characteristically symmetrical and confined to sun-exposed areas, with CASAL’S necklace around the neck
• Its classical epidemiology is instructive — it occurs in maize-eating populations, because maize niacin is bound and unavailable, and maize is low in tryptophan, from which niacin can be synthesised
• Treating maize with lime (alkali), as in traditional Central American practice, releases the bound niacin — which is why pellagra was rare there and common where maize was adopted without the accompanying technique
• In INDIA pellagra occurred in jowar (sorghum)-eating populations of the Deccan, attributed to excess leucine interfering with the conversion of tryptophan to niacin
• Pyridoxine (B6) deficiency — causes peripheral neuropathy, seizures in infants, and sideroblastic anaemia; it is most often drug-induced, classically by isoniazid, which is why pyridoxine is given with antitubercular treatment
• Folate deficiency — causes megaloblastic anaemia, and, in early pregnancy, neural tube defects
• The critical point about folate is timing — the neural tube closes by about 28 days, frequently before the woman knows she is pregnant
• Therefore supplementation must begin before conception to prevent neural tube defects, which is why periconceptional folic acid and fortification of staples are recommended — fortification being the only measure that reaches unplanned pregnancies
• Vitamin B12 deficiency — causes megaloblastic anaemia and subacute combined degeneration of the cord
• It is particularly relevant in India because B12 is found only in animal foods, so strict vegetarians and vegans are at real risk, and surveys show widespread deficiency in Indian populations
• A danger worth stating — giving folate alone to a B12-deficient patient corrects the anaemia while allowing the neurological damage to progress, so B12 status must be considered before treating megaloblastic anaemia with folate
• Vitamin C deficiency causes scurvy — bleeding gums, perifollicular haemorrhage, poor wound healing and, in infants, subperiosteal haemorrhage with pseudoparalysis
• Give thiamine before glucose in a malnourished or alcoholic patient, or Wernicke encephalopathy may be precipitated
• Folate must be periconceptional, since the neural tube closes by about twenty-eight days
• Fortification reaches unplanned pregnancies, which supplementation by its nature cannot
• Folate alone masks B12 deficiency, correcting the anaemia while the neurological damage progresses
• B12 comes only from animal foods, which makes strict vegetarians in India genuinely at risk
• Parboiling drives thiamine into the grain, which is why the traditional practice protects against beriberi
• Infantile beriberi causes a soundless cry, is rapidly fatal, and responds dramatically to thiamine
• Pellagra dermatitis is on sun-exposed skin, symmetrical, with Casal necklace around the neck
• Lime treatment releases bound niacin from maize, which is why pellagra was rare where that technique accompanied the crop
• Indian pellagra occurred with jowar, attributed to excess leucine rather than to low niacin alone
• Give pyridoxine with isoniazid, since the drug is the commonest cause of B6 deficiency in practice
• Riboflavin deficiency is commonest and mildest, showing as angular stomatitis and a magenta tongue