This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Inborn Errors of Metabolism, Subject name: Pediatrics
Not a feature of Hartnup's disease: 
Select and explain. 
A. Pellagroid skin lesion, B. Cerebellar ataxia, C. Mental retardation, D. Psychological disturbances
C: Mental retardation
Answer: C: Mental retardation 
Explanation: c. Mental retardation(Ref: Nelson's 20/e p 636-642, Ghai 8/e p 653-655)Clinical features of Hartnup disease:Most children with Hartnup defect remain asymptomaticMajor clinical manifestation in symptomatic patient is cutaneous photosensitivity: pellagra-like rash on sun exposureSome patients may have intermittent ataxia & Psychological disturbances, but mental development is usually normal.