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USMLE Metabolic Disorders

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dateluxo's version from 2016-06-17 14:26

Metabolic Disorders

NameEnzymeExcess MetabolitesDeficient MetabolitesGeneticsSxTreatment
Most common human enzyme deficiencyGlucose 6 phosphate deH2aseHb precipitatesNADPHXLRHeinz Bodies (Hb preciptations removed by phagocytes creating bite cells)
Essential fructosuriaFructokinaseFructoseemia/uriaNoneARBenign/fructoseuria/emiaNone
Fructose intoleranceAldolase BFructose 1 phosphateAvailable phosphateARHypoglycemia/jaundice/cirrhosis/vomitingDecrease fructose/sucrose
GalactosuriaGalactokinase deficiencyGalactoseNoneARBenign/galactosuria/emia/infantile cataract/failure to tract objects/social smileNone
Classic galactosemiaUridyltransferase (glucose/galactose)Galactitol/toxic metabolitesNoneARFailure to thrive/jaundice/hepatomegaly/infantile cataracts/mental retardationDecrease galactose/lactose
Lactose intoleranceLactaseLactoseNoneAge dependent and/or hereditary (africans/asians)Bloating/cramps/osmotic diarrheaAvoid dairy/lactase pills
HyperammonemiaUrea cycle enzyme deficiencies/liver diseaseAmmonia/nitrogenousAlpha Ketoglutarate depletion (from NH4+)/stopping TCAAcquired liver disease or hereditary urea cycle enzyme deficiencies (most AR)Ammonia intoxication (tremor/asterixis/slurring/somnolence/vomiting/cerebral edema/blurred vision)Limit protein/benzoate or phenylbutryrate bind amino acids for excretion/lactulose acidifies GI to trap NH4 for excretion
Most common urea cycle disorderOrnithine transcarbamoylase deficiencyAmmonia/nitrogenous/orotic acidAlpha Ketoglutarate/BUNXLRAmmonia intoxication (tremor/asterixis/slurring/somnolence/vomiting/cerebral edema/blurred vision)
PhenylketonuriaPhenylalanine hydroxylase (or cofactor tetrahydrobiopterin)Phenylalanine/phenylketones in urineNoneARMental retardation/growth retardation/seizures/fair skin/eczema/musty body odor (aromatic amino acid)Decrease phenylalanine (aspartame in NutraSweet)/increase tyrosine
Alkaptonuria/ochronosisHomogentisic acid oxidase (helps convert tyrosine to fumarate)Homogentisic acidNoneARBenign/dark connective tissue/brown sclera/urine black on exposure to air/HGA toxic to cartilage causing arthralgias
AbinismTyrosinase (contains copper)/tyrosine transportersNoneMelaning/Tyrosine (when transporters defective)Variable (ocular is XLR)Risk of skin cancerNone
Homocystinuria 1Cystathionine synthase deficiency (normally leads to cysteine)HomocysteineCysteineARMental retardation/osteoporosis/tall/kyphosis/lens subluxation/atherosclerosisCysteine essential/Decrease methionine/increase cysteine/B12/folate
Homocystinuria 2Cystathionine synthase affinity for pyridoxal phosphateHomocysteineCysteineARMental retardation/osteoporosis/tall/kyphosis/lens subluxation/atherosclerosisCysteine essential/Increase B6
Homocystinuria 3Homocysteine methyltransferase deficiency (normally leads to methionine)HomocysteineCysteineARMental retardation/osteoporosis/tall/kyphosis/lens subluxation/atherosclerosisCysteine essential
CystinuriaAmino acid transporter (Cyst/Orni/Lys/Arg) in PCTCysteineNoneARCystine (2 cysteine) hexagonal crystals/staghorn calculiHydration/urinary alkalinization
Maple Syrup Urine DiseaseAlpha ketoacid dehydrogenase (B1) decreaseBranched chain amino acids (Ile/Leu/Val)NoneARCNS defects/mental retardation/death/maple syrup urineNone
HartnupAA transporter on renal/intestinal epitheliaNoneTryptophan (loss in urine/nonabsorption from gut) resulting Niacin as wellARPellagra (Niacine/B3 deficiency/dermatitis/dementia/diarrhea)None
I Von GierkeGlucose 6 phosphataseHepatic glycogen/lactate in bloodGlucoseARSevere fasting hypoglycemia/hepatomegalyNone
II PompeLysosomal alpha 1/4 glucosidase/acid maltaseLysosomal glycogenNoneARCardiomegaly/systemic/deathNone
III CoriDebranching enzyme/alpha 1/6 glucosidaseBranched glycogenGlucoseARHypoglycemia/hepatomegalyNone
V McArdleSkeletal muscle glycogen phosphorylaseMuscle glycogenNoneARPainful muscle cramps/myoglobinuria with strenuous exerciseNone
FabryAlpha galactosidase ACeramide trihexosideNoneARPeripheral neuropathy of hands/feet/angiokeratomas/CV/renal diseaseNone
GaucherGlucocerebrosidaseGlucocerebrosideNoneARHepatosplenomegaly/aseptic femur necrosis/bone crises/Gaucher cells (macrophages like crumpled paper)None
Niemann PickSphingomyelinaseSphingomyelinNoneARProgressive neurodegeneration/hepatosplenomegaly/cherry red spot macula/foam cellsNone
Tay SachsHexosaminidase AGM2 gangliosideNoneARProgressive neurodegeneration/developmental delay/cherry red spot on macula/lysosomes with onion skin/no hepatosplenomegalyNone
KrabbesGalactocerebrosidaseGalactocerebrosideNoneARPeripheral neuropathy/developmental delay/optic atrophy/globoid cellsNone
Metachromic LeukodystrophyArylsulfatase ACerebroside sulfateNoneARCentral/peripheral demyelination w/ataxia/dementiaNone
HurlersAlpha L iduronidaseHeparan sulfate/dermatan sulfateNoneARDevelopmental delay/gargoylism/airway obstruction/corneal clouding/hepatosplenomegalyNone
HuntersIduronate sulfataseHeparan sulfate/dermatan sulfateNoneXLRMild developmental delay/gargoylism/airway obstruction/hepatosplenomegaly/aggressive behaviorNone
Carnitine deficiencyInability to transfer LCFAs into mitochondriaToxic LCFA accumulationHypoketotic hypoglycemiaN/AWeakness/hypotonia/hypoketotic hypoglycemiaNone
I hyperchylomicronemiaLipoprotein lipase deficiency/altered CIIChylomicrons/TG/CholesterolNoneARPancreatitis/hepatosplenomegaly/eruptive/pruritic xanthomas/NO increased atherosclerosisNone
IIa familial hypercholesterolemiaAbsent/decreased LDL receptorLDL/cholesterolNoneADAccelerated atherosclerosis/tendon xanthomas/corneal arcusNone
IV hypertriglyceridemiaVLDL overproductionVLDL/TGNoneADPancreatitisNone
AbetalipoproteinemiaMicrosomal triglyceride transfer protein/cannot export lipid to chylomicronsIntestinal lipidsB48/B100ARFailure to thrive/steatorrhea/acanthocytosis/ataxia/night blindnessNone
Pyruvate DeH2ase deficiencyPyruvate dehydrogenase complexPyruvate/lactateNoneX linkedLactic acidosis/Neurologic defects/usually in infancyIncrease ketogenic nutrients (fat/leucine/lysine)
KwashiorkorDietaryNoneProtein malnutritionDietaryMEAL (Malnutrition/Edema/Anemia/Liver Fatty)None
MarasmusDietaryNoneEnergy malnutritionDietaryMuscle wastingNone
SCIDAdenosine deaminaseATP/dATPDNA synthesisARLymphocytes downNone
Lesch NyhanHGPRT (converts hypoxanthine to IMP/guanine to GMP)Uric acidPurinesXLRRetardation/self mutilation/aggression/hyperuricemia/gout/choreoathetosisNone
Orotic aciduriaUMP synthase (orotic acid to UMP)Orotic acid in urine/NO hyperammonemiaUMPARMegaloblastic anemia/failure to thrive/orotic acid in urineOral uridine
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