This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: miscellaneous, Subject name: Biochemistry
Regarding Hanup disease, all are true except 
Select and explain. 
A. Associated with photosensitivity, B. Mental retardation, C. Mostly retardation, D. Mostly asymptomatic
D: Mostly asymptomatic
Answer: D: Mostly asymptomatic 
Explanation: Hanup disease is a rare genetic condition in which there is a defect of the membrane transpo mechanism for tryptophan, resulting in large losses as a result of intestinal malabsorption and failure of renal reabsorptionHanup disease reflectsImpaired intestinal and renal transpo of tryptophan and other neutral amino acids. Indole derivatives of unabsorbed tryptophan formed by intestinal bacteria are excreted. The defect limits tryptophan availability for niacin biosynthesis and accounts for the pellagra-like signs and symptoms.Which includes mental retardation Reference: Harper biochemistry, 30th edition, page no 308