Abstract

Crystal-storing histiocytosis (CSH) is a rare condition where crystals accumulate in the cytoplasm of histiocytes and is usually associated with a lymphoplasmacytic neoplasm. The most frequently involved organ systems and tissue sites include bone, head and neck, kidney, and lung. Cutaneous CSH is extraordinarily rare and limited to case reports in the literature. We report two cases of this rare disease. Case 1 was a 65-year-old male who presented to the dermatology clinic with a 4-month history of an asymptomatic indurated eruption that started as a solitary pink to skin-colored plaque on the anterior neck before progressing to involve the whole neck, chest wall, and face. The lesions were unresponsive to antihistamines or oral steroids. Case 2 was a 54 year old women with a history of unspecified “lymphoma” who presented with a soft nodule on the forearm. Biopsies from both cases had similar findings. There was a proliferation of epithelioid cells with pink cytoplasm and intracellular crystalline structures infiltrating the dermis and subcutaneous fat. These cells were positive for CD43 (1/2 cases), CD45 (1/2), and CD68 (2/2). In both cases, the tumor cells were negative for desmin, AE1/AE3, SMA, and CD34 . In case one, the crystalline structures stained positive for IgG Kappa, and in case two the structures stained positive for IgG Lambda. Cutaneous CSH is a rare dermatosis most strongly associated with lymphoplasmacytic neoplasm . The crystalline material within the histiocytes is generally of kappa light chain origin, though cases with lambda origin are reported, as in one of our cases. We bring to attention this rare diagnosis and the importance of investigating the presence of an underlying lymphoplasmacytic neoplasm.

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