This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Molecular Biology, Subject name: Biochemistry
[{'content': 'A 4 year old girl presented to hospital with failure to thrive. Her peripheral blood smear showed megaloblastic anemia. Vitamin B12 & folate were given but anemia did not improve. Enzyme assay from the cultured PBMC showed deficiency of OP (Orotate Phospho Ribosyl Transferase). What could be the probable diagnosis ? \nSelect and explain. \nA. Orotate deficiency, B. Gout, C. Orotic aciduria, D. SCID', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Orotic aciduria Due to deficiency of orotate phosphoribosyl transferase and OMP decarboxylase Leads to defect in DNA Synthesis Characterizedby : Excretion of orotic acid in urine, Severe anemia Megaloblastic Not improved with folate /vitamin B12/vitamin C Retarded growth Rx- Feeding diet rich in uridine / cytidine', 'role': 'assistant'}]