A 8 month old infant is brought to the hospital complaining that baby is losing previously acquired motor skills. Baby had hepatosplenomegaly and liver biopsy showed presence of leukocytes with intracellular sphingomyelin accumulations. what is the possible diagnosis

**Core Concept**
Infantile neurodegeneration due to lysosomal storage disorders can lead to the loss of previously acquired motor skills. Sphingomyelin accumulations in leukocytes indicate a specific enzyme deficiency responsible for sphingomyelin breakdown.

**Why the Correct Answer is Right**
The presence of sphingomyelin accumulations in leukocytes with hepatosplenomegaly is characteristic of Niemann-Pick disease, a lysosomal storage disorder caused by a deficiency of sphingomyelinase enzyme. This enzyme is responsible for breaking down sphingomyelin into ceramide and phosphocholine. Without sufficient sphingomyelinase activity, sphingomyelin accumulates in various cells, including leukocytes, leading to cellular dysfunction and organomegaly.

**Why Each Wrong Option is Incorrect**
* **Option A:** Tay-Sachs disease is another lysosomal storage disorder caused by hexosaminidase A deficiency, resulting in GM2 ganglioside accumulation, not sphingomyelin.
* **Option B:** Gaucher's disease is a lysosomal storage disorder caused by glucocerebrosidase deficiency, resulting in glucocerebroside accumulation, not sphingomyelin.
* **Option C:** Fabry's disease is a lysosomal storage disorder caused by alpha-Gal A deficiency, resulting in globotriaosylceramide accumulation, not sphingomyelin.

**Clinical Pearl / High-Yield Fact**
Niemann-Pick disease is characterized by the accumulation of sphingomyelin in various cells, leading to a range of clinical manifestations, including hepatosplenomegaly, neurodegeneration, and loss of motor skills.

**Correct Answer:** C.

✓ Correct Answer: C. Niemann Pick disease