Crystal storing histiocytosis of the skin associated with multiple myeloma

Crystal storing histiocytosis (CSH) imitating rhabdomyoma is a very rare disease entity involving different tissues. The skin is involved in extremely rare cases.

To describe the clinical and histopathological characteristics in a patient with unusually extensive skin involvement.

A 62-year-old woman presented with a large red infiltrated verrucosus lesion on the anterior aspect of the chest and on the neck. The skin biopsy revealed histiocytes throughout the whole dermis containing thin crystalloid structures in the cytoplasm. Upon histopathological examination, crystal-storing histiocytosis was diagnosed and consequently a hematological examination revealed multiple myeloma IgG Kappa. Skin involvement by CSH proceeded the diagnosis of multiple myeloma by 4 years.

Phagocytosis of crystals of immunoglobulins by histiocytes (crystals storing histiocytosis) is a rare symptom associated most often with lymphoproliferative disease. The clinical picture is not characteristic, in the histopathologic picture it is striking similarity to rhabdomyoma. The skin involvement by crystal storing histiocytosis can be the first symptom of malignant lymphoma that can proceed the hematological malignancy by years.