Generalized crystal-storing histiocytosis as a presentation of multiple myeloma: a case with a possible pro-aggregation defect in the immunoglobulin heavy chain

Crystal-storing histiocytosis (CSH) with massive accumulation of particulate immunoglobulins is a rare phenomenon accompanying B-cell dyscrasias. In the reported case (M51), the disease presented as systemic CSH and later was proved to be a frank multiple myeloma. The aggregates of crystal-laden histiocytes were demonstrated in the bone marrow, lungs, kidney, and liver. Additionally, the crystalline immunoglobulin particles were identified in renal stromal cells and in hepatocytes. The patient developed lung adenocarcinoma and died 12 months after the presentation, shortly after the lobectomy. In this paper, we report the results of morphological (including electron microscopy), immunohistochemical, and biochemical analysis. The tendency for aggregation of the IgG kappa monoclonal protein was due to the abnormal physicochemical properties of its heavy chain. Massive accumulation of crystal-storing histiocytes surpassed the myeloma tumor burden and markedly contributed to the severity of the disease.