What is the main clinical feature of Niemann-Pick disease observed in electron microscopy?

Niemann-Pick disease is characterized by the accumulation of sphingomyelin due to a deficiency of the enzyme sphingomyelinase. One of the most distinctive features observed in electron microscopy is the presence of "zebra bodies," which are membranous cytoplasmic bodies exhibiting a characteristic lamellar or zebra-striped appearance. These structures are a result of the accumulation of sphingomyelin and other lipids within the lysosomes of affected cells, particularly macrophages.

Zebra bodies are pivotal for diagnosing Niemann-Pick disease, as they are specific to this condition and help differentiate it from other lipid storage diseases. Other clinical presentations of Niemann-Pick disease may include organomegaly (such as splenomegaly or hepatomegaly), neurological deficits, and in some cases, failure to thrive. However, from a microscopic perspective, the identification of zebra bodies is a definitive hallmark of the disease.

In contrast, while options such as lipid droplets, fatty infiltration, or giant cells relate to various disorders or pathologies, they do not provide the same specific indication that zebra bodies do for Niemann-Pick disease. Thus, the presence of zebra bodies underscores the unique pathology seen in this condition.