Splenomegaly With Thrombocytopenia: A Case of the Rare and Obvious

A 12-year-old boy presented with incidental splenomegaly, mild anemia, and thrombocytopenia, prompting evaluation, with Gaucher disease considered in the differential diagnosis.

Enzyme testing revealed low β-glucosidase activity twice; however, Sanger sequencing was negative for mutations in the glucocerebrosidase 1 (GBA1) gene. A peripheral smear review was the turning point; it showed stomatocytes and giant platelets, suggestive of sitosterolemia. Next-generation sequencing confirmed a homozygous, likely pathogenic variant in ATP-binding cassette subfamily G member 5 (ABCG5). The child was started on Ezetimibe and a low plant-sterol diet.

This case reiterates the importance of peripheral smear examination in leading to a very specific yet uncommon diagnosis of sitosterolemia.