Crystal-storing histiocytosis: a rare lesion in periapical pathology.

Crystal-storing histiocytosis is a rare manifestation of plasma cell dyscrasia/monoclonal gammopathies and lymphoproliferative disorders, characterized by cytoplasmic accumulation of crystallized immunoglobulins in histiocytes. Nevertheless, some reported cases of crystal-storing histiocytosis raise the possibility that this lesion may also be reactive. Crystal-storing histiocytosis in the oral cavity is extremely rare; only one case affecting the tongue has been reported in the English-language literature. In this report, we discuss the case of a 38-year-old man who presented a persistent periapical lesion affecting the maxillary left lateral incisor. Histopathological analysis showed numerous crystal-laden histiocytes associated with a mild plasma cell infiltrate within a fibrous stroma. The plasma cells failed to show clonal light-chain restriction, and the patient had no associated hematologic disorder or systemic disease. Thus, this lesion was probably the result of hypersecretion of immunoglobulins by polyclonal plasma cells found in the periapical lesion. Crystal-storing histiocytosis should be considered in the differential diagnosis of periapical lesions.