Glycogen storage disease type III



Glycogen storage disease type III



Glycogen storage disease type III


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USMLE® Step 1 questions

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Glycogen storage disease type III

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USMLE® Step 1 style questions USMLE

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A 1-year-old girl is brought to the clinic for evaluation of poor growth and poor muscle tone. The mother states that the patient “doesn’t seem to be gaining weight,” despite adequate feedings. Temperature is 36.4°C (97.5°F), pulse is 98/min, blood pressure is 104/64, and respiratory rate is 35/min. Motor examination reveals diffuse hypotonia in all 4 limbs. Abdominal examination reveals hepatomegaly. Rapid fingerstick glucose is 40 mg/dL. Echocardiogram reveals left ventricular hypertrophy. Serum lactate levels are within normal limits. A liver biopsy reveals widespread fibrosis with minimal fat infiltration. Further analysis reveals accumulation of limit dextrin-like complexes in the cytosol of hepatocytes. Which of the following is the most likely diagnosis? 

External References

First Aid








Cori disease p. 85

Debranching enzyme

Cori disease p. 85


Glycogen storage disease type III is one of the genetic disorders affecting how the body stores and uses glycogen. People with glycogen storage disease type III have a deficiency of the glycogen debrancher enzyme (α-1,6-glucosidase), one of the enzymes that help to break down glycogen. The symptoms of glycogen storage disease type III generally appear during childhood and include generalized muscle weakness, hepatosplenomegaly, fasting hypoglycemia, and ketosis.


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