Question 1

Q: A 6-month-old infant presents with severe hypoglycemia, hepatomegaly, and lactic acidosis. Physical examination reveals a doll-like face with fat cheeks and protuberant abdomen. Laboratory studies show elevated serum lactate, uric acid, and triglycerides. A liver biopsy demonstrates excessive glycogen accumulation. Glucagon administration fails to increase blood glucose levels. Apply your knowledge to determine the most likely enzymatic defect.

Glucose-6-phosphatase deficiency. ***Glucose-6-phosphatase deficiency*** - This infant presents with **Von Gierke disease (GSD Type I)**, characterized by an inability to convert **glucose-6-phosphate to glucose**, impairing both **glycogenolysis** and **gluconeogenesis**. - Clinical hallmarks include **severe fasting hypoglycemia**, **hepatomegaly**, **lactic acidosis** (due to decreased lactate clearance), and **hyperuricemia**, with a characteristic **doll-like face** due to fat deposition. *Muscle phosphorylase deficiency* - Also known as **McArdle disease (GSD Type V)**, this condition affects skeletal muscle and presents with **exercise intolerance**, muscle cramps, and **myoglobinuria**. - It does not cause **hypoglycemia** or **hepatomegaly**, as the liver enzyme remains functional. *Debranching enzyme deficiency* - Deficiency results in **Cori disease (GSD Type III)**, which presents with hepatomegaly and milder hypoglycemia than Type I. - Key differentiators are the presence of **normal blood lactate levels** and the fact that **gluconeogenesis** is preserved. *Lysosomal alpha-glucosidase deficiency* - Known as **Pompe disease (GSD Type II)**, this is a lysosomal storage disorder that primarily causes massive **cardiomegaly** and systemic **hypotonia**. - It typically does not present with **hypoglycemia** because cytoplasmic glycogenolysis is still functional. *Branching enzyme deficiency* - Known as **Andersen disease (GSD Type IV)**, it typically presents in early infancy with progressive **liver cirrhosis** and failure. - This condition is characterized by the accumulation of **abnormal glycogen (amylopectin-like)** rather than excessive normal glycogen, and it lacks the severe lactic acidosis seen here.

Question

A 6-month-old infant presents with severe hypoglycemia, hepatomegaly, and lactic acidosis. Physical examination reveals a doll-like face with fat cheeks and protuberant abdomen. Laboratory studies show elevated serum lactate, uric acid, and triglycerides. A liver biopsy demonstrates excessive glycogen accumulation. Glucagon administration fails to increase blood glucose levels. Apply your knowledge to determine the most likely enzymatic defect.

Accepted Answer

Glucose-6-phosphatase deficiency

Answer

Branching enzyme deficiency

Answer

Muscle phosphorylase deficiency

Answer

Lysosomal alpha-glucosidase deficiency

Answer

Debranching enzyme deficiency

Glycogen storage diseases — MCQs

Glycogen storage diseases — MCQs

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