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Flashcards in Metabolic - Diseases Deck (18):

Rickets / Osteomalacia

Results from Vitamin D deficiency in children / adults, respsectively; presents as bony deformity and bone pain (Rickets) with progressive softening of bones (osteomalacia)

Labs: Hypocalcemia, hypophosphatemia, elevated ALP, elevated PTH

Findings: Chvostek's sign, Trousseau sign

Treatment: Vitamin D supplementation


Maple Syrup Urine Disease

Autosomal recessive defect in alpha-ketodehydrogenase, responsible for the metabolism of branched amino acids (Leucine, Isoleucine, Valine)

Results in increased alpha-ketoacids in the blood

Presents with sweet-smelling urine, severe CNS abnormalities/intellectual disability, and death in infancy

Treatment: Dietary restriction of branched AAs; thiamine supplementation


Tay Sach's Disease

Autosomal recessive deficiency of Hexosaminidase A responsible for conversion of GM2 ganglioside to GM3 ganglioside

Presents with progressive neurodegeneration, intellectual disability, "cherry red spot" on the macula

NO hepatosplenomegaly


Niemann-Pick Disease

Autosomal recessive deficiency of sphingomyelinase, with accumulation of sphingomyelin

Presents with progressive neurodegeneration, intellectual disability, "cherry red spot" on the macula PLUS hepatosplenomegaly



Vitamin C deficiency, necessary for hydroxylation of proline and lysine in collagen synthesis

Presents with bleeding, petechiae, swollen gums, hemarthroses, and "corkscrew hair"


Hunter Syndrome

X-linked recessive deficiency of iduronate sulfatase

Affected males present with mild intellectual disability, hearing loss, coarse facies, hepatosplenomegaly

NO corneal clouding (vs. Hurler syndrome)


Hurler Syndrome

Autosomal recessive defect of alpha iduronidase; boys and girls affected equally

Presents with developmental delay, airway obstruction, hepatosplenomegaly + corneal clouding


Essential fructosuria

Autosomal recessive defect in fructokinase causing benign, asymptomatic presence of fructose in the blood and urine


Fructose intolerance

Autosomal recessive Aldolase B deficiency; causes accumulation of Fructose-1-Phosphate, which diminishes stores of available phosphate; decreased phosphate inhibits glycogenolysis and gluconeogenesis

Presents with hypoglycemia, jaundice, and vomiting following ingestion of fruit, juice, and honey

Dx: Reducing sugars in urine (non-specific)

Treatment: Reduced dietary intake of fructose and sucrose


Galactokinase Deficiency

Autosomal recessive; leads to accumulation of Galactitol via shunting down an alternative metabolic pathway

Relatively mild; presents with infantile cataracts + galactose in blood and urine



Autosomal recessive defect in Galactose-1-Phosphate Uridyltransferase leads to depletion of phosphate stores and accumulation of toxic metabolites including Galactitol

Presents with failure to thrive, jaundice, hepatomegaly, infantile cataracts, and intellectual disability

Treatment - elimination of dietary galactose and lactose (including breast milk and lactose-containing formulas)


Porphyria Cutanea Tarda

Most common porphyria

Due to defect of uroporphyrinogen decarboxylase enzyme of heme biosynthetic pathway, resulting in accumulation of uroporphyrin

Presents with blistering cutaneous photosensitivity and tea-colored urine


Acute Intermittent Porphyria

Second most common porphyria; due to deficiency of enzye porphobilinogen deaminase with accumulation of porphobilinogen

Presentation - 5Ps: Painful abdomen, port wine-colored urine, polyneuropathy, psych disturbances, precipitated by alcohol, drugs, or starvation

Treated with glucose and heme



Autosomal recessive deficiency of homogentisic oxidase, an enzyme in the tyrosine degradation pathway

Accumulation of homogentisic acid leads to dark pigmentation of connective tissue (sclerae, pinnae); usually benign but sometimes associated with arthralgias

Findings: Urine turns black upon standing


Milk Alkali Syndrome

Hypercalcemia + Metabolic alkalosis + Renal insufficiency

Presents with fatigue, depressed mood, muscle weakness, constipation/abdominal pain; commonly occurs secondary to OTC Ca-containing antacid use

Findings: High calcium, low phosphate, low potassium, high bicarbonate, high BUN, high CrCl


I-cell disease

Lysosomal storage disease caused by deficiency in the enzyme responsible for phosphorylation of mannose residues on glycoproteins; results in inappropriate extracellular secretion of proteins that should be targeted to the lysosome

Presents with coarse facial features, corneal clouding, restricted joint movement; often fatal in childhood

Labs show increased levels of lysosomal enzymes in the blood



Caused by Vitamin B3 (Niacin) deficiency

Presents with dermatitis, diarrhea, and dementia

May occur as a result of insufficient dietary intake or inherited defect in metabolism leading to decreased tryptophan


Hartnup's Disease

Inherited disorder of renal tubular reabsoroption of neutral amino acids, most significantly Tryptophan (precursor to Niacin)

Causes pellagra