21 - iced

[ArchivalUser]

A 24-year-old graduate student presents to a physician with complaints of severe muscle cramps and weakness
with even mild exercise. Muscle biopsy demonstrates glycogen accumulation, but hepatic biopsy is unremarkable.
Which of the following is the most likely diagnosis?


A. Hartnup's disease

B. Krabbe's disease

C. McArdle's disease

D. Niemann-Pick disease

E. Von Gierke's disease

[ArchivalUser]

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[ArchivalUser]

very good....................... The correct answer is C. A variety of glycogen storage diseases exist, corresponding to defects in different
enzymes in glycogen metabolism; most of these involve the liver. McArdle's disease (Type V glycogen storage
disease), due to a defect in muscle phosphorylase, is restricted to skeletal muscle. The presentation described
in the question stem is typical. Many affected individuals also experience myoglobinuria. Definitive diagnosis is
based on demonstration of myophosphorylase deficiency.

Hartnup's disease (choice A) is a disorder of amino acid transport.

Krabbe's disease (choice B) is a lysosomal storage disease.

Niemann-Pick disease (choice D) is a lysosomal storage disease.

Von Gierke's disease (choice E) is a glycogen storage disease with prominent involvement of liver, intestine,
and kidney.