Metabolic Disorders, NEET PG & INI-CET Biochemistry MCQs

Explanation

Von Gierke disease, glycogen storage disease type I, is due to glucose-6-phosphatase deficiency, blocking the final step of gluconeogenesis and glycogenolysis. This causes fasting hypoglycaemia, hepatomegaly and lactic acidosis.

Explanation

McArdle disease, glycogen storage disease type V, results from muscle glycogen phosphorylase deficiency, causing exercise intolerance, cramps and myoglobinuria, with a characteristic second wind as fatty acids are recruited.

Explanation

Phenylketonuria is caused by phenylalanine hydroxylase deficiency, leading to phenylalanine accumulation, a musty odour, fair pigmentation and intellectual disability if untreated. Management is a phenylalanine-restricted diet.

Explanation

Alkaptonuria is due to homogentisate oxidase deficiency, causing accumulation of homogentisic acid. Urine darkens on standing, and pigment deposits in connective tissue cause ochronosis and arthritis.

Explanation

Classic galactosaemia results from galactose-1-phosphate uridyltransferase deficiency. Galactose-1-phosphate accumulates, causing liver damage, cataracts and, if untreated, sepsis. Treatment is a galactose-free diet.

Explanation

Tay-Sachs disease is caused by hexosaminidase A deficiency, leading to GM2 ganglioside accumulation, neurodegeneration and a cherry-red macular spot. Unlike Niemann-Pick disease, there is no hepatosplenomegaly.

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Gaucher disease is the most common lysosomal storage disorder, due to glucocerebrosidase deficiency. Gaucher cells, lipid-laden macrophages with a crumpled tissue paper appearance, accumulate and cause hepatosplenomegaly and bone disease.

Explanation

Maple syrup urine disease is due to deficient branched-chain ketoacid dehydrogenase, causing accumulation of leucine, isoleucine and valine. It presents with a characteristic urine odour, poor feeding and neurological decline.

Explanation

Wilson disease is a disorder of copper metabolism with low ceruloplasmin, causing copper accumulation in the liver, brain and cornea, where it forms Kayser-Fleischer rings. Treatment uses copper chelators such as penicillamine.

Explanation

G6PD deficiency, an X-linked disorder, reduces NADPH and leaves red cells vulnerable to oxidative stress. Triggers such as fava beans, infections and drugs like primaquine cause haemolysis with bite cells and Heinz bodies.

Explanation

Homocystinuria, most often from cystathionine beta-synthase deficiency, causes a marfanoid habitus, downward lens dislocation, thromboembolism and intellectual disability. In Marfan syndrome the lens dislocates upward and there is no thrombotic tendency.