An infant presented to the OPD with a history of vomiting and malnutrition. Patient has blue eyes, blonde hair & fair skin. On investigation, Guthrie test was found to be positive. All are true regarding this disease EXCEPT:
(A) Due to PAH enzyme defect (B) White patch of hair due to tryptophan deficiency (C) Phenyl acetate positive in urine (D) Mental retardation is present
(B) This is Phenyl-ketonuria. Guthrie's bacterial inhibition test is a screening test for phenylketonuria (PKU), used to detect the abnormal presence of phenylalanine metabolites in blood i.e. Phenyl pyruvate, Phenyl alanine & Phenyl-lactate. FeCl3 detects phenyl alanine levels in urine. WITH REGARDS TO OTHER OPTIONS In Phenylketonuria, Phenylalanine is accumulated due to deficiency of enzyme Phenylalanine Hydroxylase. As a result Phenylalanine is not conveed to Tyrosine and is responsible for mental retardation in patients. Tyrosine becomes essential in these patients. CILINICAL MANIFESTATION CNS - Mental retardation, failure to walk and talk, growth retardation, seizures, tremors, microcephaly. Pigmentation - melanin is synthesized from tyrosine. so in PKU melanin is less result in hypopigmentation that cause light skin colour, blue eyes, fair hair Treatment - low phenylalanine content diet