False about hanup's disease: (A) Defect in neutral aminoacid transpo, (B) Mental retardation is the common presentation, (C) Most children are asymptomatic, (D) Photosensitivity
Answer is B. It is a rare inborn error of metabolism with autosomal recessive inheritance. Neutral amino acids, including tryptophan, are not transpoed across the brush border epithelium of the intestine and kidneys, This results in deficiency of synthesis of nicotinamide It causes a photo-induced pellagra-like syndrome. Cutaneous signs precede neurologic manifestations Eczematous, occasionally vesiculobullous eruption noted on the face and extremities in a glove-and-stocking photodistribution. Neurologic symptoms are fully reversible. Administration of nicotinamide and protection from sunlight improves both cutaneous and neurologic manifestations.