**Question:** Enzyme deficiency in Cori disease is

A. fructose-1,6-bisphosphatase deficiency
B. glucose-6-phosphate dehydrogenase deficiency
C. lactate dehydrogenase deficiency
D. glucose-6-phosphate transporter deficiency

**Correct Answer:** A. fructose-1,6-bisphosphatase deficiency

**Core Concept:** Cori disease is a disorder characterized by impaired glucose homeostasis, resulting from deficiency in the enzyme fructose-1,6-bisphosphatase. This enzyme is a key component of the Cori cycle, a series of reactions that regulate glucose and ammonia levels in the body.

**Why the Correct Answer is Right:** Fructose-1,6-bisphosphatase deficiency leads to a decrease in the rate of gluconeogenesis, a process that generates glucose from non-carbohydrate sources. Consequently, blood glucose levels increase (hyperglycemia) and ammonia levels become elevated (hyperammonemia), leading to the clinical manifestations of Cori disease.

**Why Each Wrong Option is Incorrect:**

A. Glucose-6-phosphatase deficiency is a separate enzyme involved in the same cycle, gluconeogenesis. This option is incorrect because it is another enzyme involved in glucose homeostasis rather than fructose-1,6-bisphosphatase.

B. Glucose-6-phosphate dehydrogenase deficiency affects an enzyme involved in the pentose phosphate pathway, not gluconeogenesis or the Cori cycle. It is related to oxidative stress and hemolysis rather than glucose homeostasis.

C. Lactate dehydrogenase deficiency pertains to lactate and pyruvate interconversion, which is unrelated to the Cori cycle and glucose homeostasis. This option is incorrect because it involves another enzyme involved in energy production pathways rather than gluconeogenesis.

D. Glucose-6-phosphate transporter deficiency is a separate mechanism related to glucose transport across cellular membranes, not involved in the Cori cycle or glucose homeostasis. This option is incorrect because it is a transport mechanism rather than an enzyme involved in glucose production.

**Clinical Pearl:** Cori disease is a rare genetic disorder that primarily affects the liver and kidneys. Patients may present with symptoms like hepatomegaly, hyperammonemia, and hyperglycemia. Diagnosis is typically confirmed through genetic testing, as symptoms overlap with other disorders. Treatment typically involves managing hyperammonemia, hyperglycemia, and liver dysfunction through supportive care and, in severe cases, liver transplantation.