Benign signet ring cells in the subserosa of the small intestine: a pseudoneoplastic phenomenon

pyrazinamide, isoniazide, 6-mercaptopurine and 5-flurouracil may also result in pellagra like syndromes. Pyrazinamide and isonicotinic acid hydrazide (INH) are structural analogues of niacin and can depress endogenous niacin production by feedback inhibition or substrate competition. INH impairs the functioning of pyridoxine, a cofactor in tryptophan-niacin pathway and inhibits the niacin synthesis leading to pellagra. 2 Dermal pathogenesis reveals lowered collagen and urocanic acid content, serving as a filter for ultraviolet radiation, may cause photosensitive pellagra dermatitis. Chromatolytic changes are found in Betz cells of motor cortex. Similar cerebellar changes, optic neuropathy and cerebral deficit seen in pellagra encephalopathy may not resolve completely even with high doses of niacin. The diagnosis of pellagra is clinical. Laboratory diagnosis by fluorometric assay of urinary metabolites (2-pyridone/ N-methylniacinamide ratio less than 2.0) is not unequivocal evidence of pellagra. The recommended daily allowance is 10-20mg/day. Since niacin causes flushing, headache, burning and tingling sensations, niacinamide is prescribed orally (300-500 mg) and parenterally (100 mg per day) in divided doses. Neuropsychiatric manifestations are relieved dramatically overnight. Topically zinc oxide and para-aminobenzoic acid ointment may be advised. Conclusion: Physicians should be aware of such cases and should treat any " sick " person with unexplained skin, neuro-psychiatric changes or gastrointestinal complaints with safe, inexpensive doses of niacin.