A 78-year-old woman with hypertrophic cardiomyopathy underwent a septal myomectomy and valve replacement. In the immediate postoperative period she developed shock of mixed etiology and died. At autopsy, hepatomegaly and splenomegaly were identified, with PAS and Giemsa positive intracellular ceroid granular deposits. Sea-blue histiocytosis is an extremely rare, chronic and benign deposit disease. It is characterized by hepatosplenomegaly, thrombocytopenia and lymphadenopathy. The presence of ceroid substance in granules in PAS and Giemsa stains should establish the diagnosis of suspicion.