**Question:** Hepatospleenomegalv with Foam cells is characteristically seen in a Lysosomal disorder. This disorder is due to the deficency of

A. Acetyl-CoA carboxylase
B. Sphingomyelinase
C. Glucose-6-phosphatase
D. Cysteine protease

**Correct Answer:** .

**Core Concept:**
Lysosomes are membrane-bound organelles found in eukaryotic cells that contain hydrolytic enzymes responsible for the degradation of various cellular components, such as lipids, proteins, and nucleic acids. Lysosomal disorders are a group of inherited diseases characterized by the accumulation of undigested cellular waste products due to lysosomal enzyme deficiencies.

**Why the Correct Answer is Right:**
The correct answer is B (Sphingomyelinase). Sphingomyelinase deficiency is a lysosomal storage disorder that results in the accumulation of sphingomyelin and cholesterol in hepatosplenomegaly, leading to the formation of foam cells. These foam cells are characterized by the presence of numerous lipid droplets, which can be visualized microscopically in the liver and spleen.

**Why Each Wrong Option is Incorrect:**
A. Acetyl-CoA carboxylase (option A) is involved in the synthesis of fatty acids, which is not related to the lysosomal storage disorders causing hepatosplenomegaly with foam cells.

C. Glucose-6-phosphatase (option C) is involved in the regulation of glucose uptake in the liver, not lysosomal storage disorders.

D. Cysteine protease (option D) is an enzyme involved in protein degradation, unrelated to lysosomal storage disorders.

**Clinical Pearl:**
Hepatosplenomegaly with foam cells is a characteristic feature of lysosomal storage disorders like Niemann-Pick disease, which is caused by the deficiency of sphingomyelinase or other lysosomal enzymes. These disorders are a result of the accumulation of lipids in various tissues, leading to organ dysfunction and enlargement. Recognizing the presence of hepatosplenomegaly and foam cells in clinical practice can help differentiate these disorders from other conditions with similar presentations, such as viral hepatitis or hemochromatosis.

**Why the Correct Answer is Right:**
Sphingomyelinase deficiency (option B) is a lysosomal storage disorder that results in the accumulation of sphingomyelin and cholesterol in the liver, spleen, and other tissues. The accumulation of these lipids leads to hepatosplenomegaly and the presence of foam cells, which are characterized by numerous lipid droplets in the cytoplasm of hepatocytes and macrophages.

**Why Each Wrong Option is Incorrect:**
Acetyl-CoA carboxylase (option A) is involved in fatty acid synthesis, not in lysosomal storage disorders that cause hepatosplenomegaly with foam cells.

Glucose-6-phosphatase (option C) is involved in glucose regulation, which is unrelated to lysosomal storage disorders.

Cysteine protease (option D