A four-year-old child with exercise intolerance. On investigation Blood pH 7.3, FBS 60 mg%, hypertriglyceridemia, ketosis and lactic acidosis. The child had hepatomegaly and renomegaly. Biopsy of liver and kidney showed increased glycogen content. What is the diagnosis?
**Core Concept**
The child's symptoms and lab findings point to a disorder of glycogen metabolism, involving impaired glycogen breakdown and accumulation of glycogen in the liver and kidneys. This condition leads to hypoglycemia, lactic acidosis, and ketosis due to the body's inability to utilize glucose for energy.
**Why the Correct Answer is Right**
The child's presentation is consistent with McArdle's disease (Glycogen storage disease type V), caused by a deficiency of the enzyme myophosphorylase. However, the biopsy findings of increased glycogen content in the liver and kidneys suggest a different diagnosis. The accumulation of glycogen in these organs, combined with the child's symptoms, is indicative of Glycogen storage disease type IV (Andersen's disease), caused by a deficiency of the enzyme branching enzyme (BE). This enzyme is responsible for the correct branching of glycogen molecules, allowing for their proper breakdown. In its absence, glycogen becomes abnormally large and insoluble, leading to its accumulation in the liver and kidneys.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the scenario described, as it does not involve glycogen metabolism or accumulation.
* **Option B:** Pompe disease (Glycogen storage disease type II) is caused by a deficiency of the enzyme acid alpha-glucosidase, leading to glycogen accumulation in lysosomes, not the liver and kidneys.
* **Option C:** Cori's disease (Glycogen storage disease type III) is caused by a deficiency of the debranching enzyme, leading to glycogen accumulation in the liver and muscles. However, the child's biopsy findings of increased glycogen content in the liver and kidneys do not match this diagnosis.
**Clinical Pearl / High-Yield Fact**
Glycogen storage diseases can be classified based on the enzyme deficiency and the affected organs. It is essential to consider the clinical presentation, lab findings, and biopsy results to determine the specific type of glycogen storage disease.
**Correct Answer:** D.