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What is Mental retardation is a clinical feature of: and explain in detail?
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 (s)ConditionEnzyme 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 (benign)ARTyrosineTyrosinemia type I (hepatorenal)Fumarylacetoacetate hydrolaseLiver failure, cirrhosis, rickets, failure to thrive, peripheral neuropathy, "boiled cabbage" odorAR Tyrosinemia type II (oculocutaneous)Tyrosine 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 (oculocutaneous)TyrosinaseHypopigmentation of hair, skin, and optic fundus; visual loss; photophobiaAR Albinism (ocular)Different enzymes or transportersHypopigmentation of optic fundus, visual lossAR, XL DOPA-responsive dystoniaTyrosine hydroxylaseRigidity, truncal hypotonia, tremor, intellectual disabilityAR