Metabolism Quiz

Enzyme deficiencies

The diseases exams reach for when they want to test a pathway backwards: remove one enzyme and predict what accumulates, what is missing, and what the patient looks like. Each page explains the why, not just the pairing.

Hypothalamic GnRH neurons
Kallmann syndrome — Puberty never starts, and the patient cannot smell
Glucose-6-phosphatase
Von Gierke disease (GSD I) — Severe fasting hypoglycemia, enlarged liver, lactic acidosis, high uric acid and lipids
Muscle glycogen phosphorylase
McArdle disease (GSD V) — Exercise intolerance and cramps, dark urine after exertion, and a characteristic second…
Glucose-6-phosphate dehydrogenase
G6PD deficiency — Episodic hemolytic anemia after fava beans, sulfa drugs, antimalarials or infection
Pyruvate kinase
Pyruvate kinase deficiency — Chronic hemolytic anemia from birth, with splenomegaly and jaundice
Medium-chain acyl-CoA dehydrogenase
MCAD deficiency — Vomiting, lethargy and coma during a fast or illness in a young child
Ornithine transcarbamoylase
OTC deficiency — Hyperammonemia, vomiting, lethargy and cerebral edema, often after a protein load
Aldolase B
Hereditary fructose intolerance — Vomiting, hypoglycemia and jaundice appearing when an infant is weaned onto fruit or…
Phenylalanine hydroxylase
Phenylketonuria — Intellectual disability, seizures, fair skin and hair, and a musty body odor
Pyruvate dehydrogenase
PDH deficiency — Lactic acidosis from birth with neurological impairment, worsened by a high-carbohydrate…
Galactose-1-phosphate uridyltransferase
Classic galactosemia — Jaundice, hepatomegaly, cataracts and E. coli sepsis in a neonate on milk
Adrenal cortex
Addison disease — Fatigue, weight loss, low blood pressure, salt craving and darkening skin
Dietary iodine
Endemic goiter — A visibly enlarged thyroid with fatigue, cold intolerance and weight gain
Lactase
Lactose intolerance — Bloating, cramps and diarrhea after dairy
Control points reference Daily quiz