Sea-blue histiocytosis and thrombocytopenia successfully treated with an mTORC1 inhibitor: a case report.

This report describes a pediatric patient with acquired sea-blue histiocytosis (SBH) and refractory immune thrombocytopenia (ITP) who harbors a heterozygous variant in TSC2 (p.Arg1713His). The child failed to respond to conventional first-line therapies for ITP but achieved rapid platelet normalization within 1 months of sirolimus initiation. Regression of SBH was observed at 3 months post-treatment. The identification of the TSC2 variant, along with the dramatic resolution of both SBH and thrombocytopenia upon sirolimus therapy, suggests a possible association between TSC2-related mTOR pathway dysregulation, sea-blue histiocytosis, and thrombocytopenia.