<prompt> Mental retardation is a clinical feature of:AlkaptonuriaAlbinismHawkinsinuriaPhenylketonuria  <response>: Ans. d PhenylketonuriaRef: Harrisons 20th ed. P 3015 - 16Phenylketonuria MC metabolic disorder of amino acid Seen due to deficiency of enzyme: Phenylalanine Hydroxylase Increased phenylalanine in blood - metabolized to phenylketones - excreted in urine - hence the name Phenylketonuria PKU. MC organ damaged due to phenylalaninemia: BrainClinical Feature Gradual development of mental retardation intellectual disability Infants normal at birth Excessive vomiting Autistic, choreiform movement Unpleasant, musty odorDiagnosis Guthrie test-screening test in blood sample Ferric chloride test: Screening test in urine sample Tandem mass spectrometry: IOCInherited disorders of Amin Acid MetabolismAmino Acid sConditionEnzyme DefectClinical FindingsInheritancePhenylalanineDNAJC12 DeficiencyHydroxylase Co-chaperoneDystonia, parkinsonism, intellectual disabilityAR PhenylketonuriaPhenylalanine hydroxylaseIntellectual disability, microcephaly, hypopigmented skin and hairs, eczema, mousy odorAR DHPR deficiencyDihydroptendine reductaseintellectual disability, hypotonia, spasticity, myoclonusAR PTPS deficiency6-Pyruvoyl- tetrahydropterin synthaseDystonia, neurologic deterioration, seizures, intellectual disabilityAR GTP cyclohydrolase I deficiencyGTP cyclohydrolase 1Intellectual disability, seizures, dystonia, temperature instabilityAR Carbinolamine dehydratase deficiencyPterin-4a carbinolamine dehydrataseTransient hyperphenylalaninemia benignARTyrosineTyrosinemia type I hepatorenalFumarylacetoacetate hydrolaseLiver failure, cirrhosis, rickets, failure to thrive, peripheral neuropathy, boiled cabbage odorAR Tyrosinemia type II oculocutaneousTyrosine transaminasePalmoplantar keratosis, painful corneal erosions with photophobia, learning disabilityAR Tyrosinemia type III4-Hydroxyphenyl pyruvate dioxygenaseHypertyrosinemia with normal liver function, occasional mental delayAR Hawkinsinuria type III4-Hydroxyphenyl pyruvate dioxygenaseTransient failure to thrive, metabolic acidosis in infancyAD AlkaptonuriaHomogentisic acid oxidaseOchronosis, arthritis, cardiac valve involvement, coronary artery calcificationAR Albinism oculocutaneousTyrosinaseHypopigmentation of hair, skin, and optic fundus; visual loss; photophobiaAR Albinism ocularDifferent enzymes or transportersHypopigmentation of optic fundus, visual lossAR, XL DOPA-responsive dystoniaTyrosine hydroxylaseRigidity, truncal hypotonia, tremor, intellectual disabilityAR 