A 28-year-old Ashkenazi Jewish woman presents with progressive hepatosplenomegaly, bone pain in the left hip, and recent pancytopenia (Hb 9.2 g/dL, platelets 85,000/μL). Bone marrow aspirate reveals lipid-laden macrophages with a characteristic "crumpled tissue paper" appearance. Imaging of the femur shows the classic "Erlenmeyer flask" deformity of the distal femur. The enzyme deficiency responsible for this presentation is the structure marked **B** in the diagram. Which of the following best describes the primary biochemical consequence of this enzyme deficiency?

Explanation

## Why "Accumulation of glucocerebroside in macrophages and subsequent formation of Gaucher cells" is right Glucocerebrosidase (β-glucosidase), the enzyme marked **B**, catalyzes the hydrolysis of glucocerebroside to glucose and ceramide. Deficiency of this enzyme in Gaucher disease (autosomal recessive) leads to pathologic accumulation of glucocerebroside within macrophages throughout the reticuloendothelial system (bone marrow, spleen, liver). These lipid-laden macrophages are the pathognomonic "Gaucher cells," characterized by the crumpled tissue paper or wrinkled silk appearance of their cytoplasm. This accumulation directly explains the clinical triad: hepatosplenomegaly (from macrophage infiltration), pancytopenia (from bone marrow replacement), and bone disease including avascular necrosis and Erlenmeyer flask deformity. The patient's presentation—Ashkenazi Jewish ancestry, hepatosplenomegaly, pancytopenia, bone involvement, and bone marrow findings—is classic for Type 1 Gaucher disease, the most common lysosomal storage disease and most common Jewish genetic disorder (Robbins 10e Ch 6; Harrison 21e Ch 411). ## Why each distractor is wrong - **Accumulation of sphingomyelin in neurons leading to progressive dementia and seizures**: This describes Niemann-Pick disease (sphingomyelinase deficiency, marked **C**), which causes CNS involvement with neurodegeneration. Gaucher Type 1 has NO CNS involvement; neurologic forms (Types 2 and 3) are rare and not the most common presentation. - **Accumulation of globotriaosylceramide in vascular endothelium causing renal and cardiac dysfunction**: This describes Fabry disease (α-galactosidase A deficiency, marked **D**), an X-linked lysosomal storage disease with vascular and renal manifestations. The clinical picture does not fit. - **Accumulation of GM2 ganglioside in neurons causing cherry-red spot on macula and developmental regression**: This describes Tay-Sachs disease (hexosaminidase A deficiency, marked **A**), which presents in infancy with severe CNS involvement, developmental regression, and ophthalmologic findings. The patient's age and clinical presentation are inconsistent with Tay-Sachs. **High-Yield:** Gaucher disease = glucocerebrosidase deficiency → Gaucher cells (crumpled tissue paper) in bone marrow/spleen/liver → hepatosplenomegaly + pancytopenia + bone disease (Erlenmeyer flask deformity). Type 1 is most common LSS overall and most common Jewish genetic disease. Treat with imiglucerase (enzyme replacement therapy). [cite:Robbins 10e Ch 6; Harrison 21e Ch 411]