CPC13 Cutaneous crystal storing histiocytosis

Abstract

Abstract A 43-year-old woman presented with a 3-year history of a gradually enlarging lesion on the right upper chest. Her comorbidities included ankylosing spondylitis and recurrent anterior uveitis, and she was taking no regular medications. She had no systemic symptoms. She was initially seen by the breast team, who organized an ultrasound that showed chronic inflammation, and a biopsy that showed granulomatous chronic inflammatory tissue. Topical treatment with fucidin was unsuccessful, and she was referred to dermatology. On examination, she had a 3.5 × 4 cm pink subcutaneous nodule on the right upper anterior chest. There was no lymphadenopathy or organomegaly. Investigations revealed low IgA (0.71 g L−1), raised IgM (4.30 g L−1) and mild thrombocytopenia (141 × 109 cells L−1). Full blood count; urea and electrolytes; liver function tests; IgG; lactate dehydrogenase; thyroid stimulating hormone; serum angiotensin-converting enzyme; autoimmune serology, including antinuclear antigen; Borrelia serology; tuberculosis QuantiFERON; ferritin; erythrocyte sedimentation rate; serum protein electrophoresis and urine Bence Jones protein were normal or negative. Chest X-ray and computed tomography of the thorax, abdomen and pelvis did not reveal any evidence of underlying malignancy. Repeat skin biopsy showed a superficial and deep dermal histiocytic infiltrate. At high power, numerous needle-like eosinophilic crystals were seen within the histiocytes. There was a periadnexal and perifollicular infiltrate of lymphocytes and plasma cells. Light chain staining showed that the plasma cells were lambda light chain restricted and were IgM positive and IgG negative. The features were of a crystal-storing histiocytosis. Cutaneous crystal-storing histiocytosis is a rare condition, with only six reported cases. The pathophysiology involves the accumulation of crystalline material within the cytoplasm of histiocytes. It is strongly associated with an underlying haematological malignancy, including multiple myeloma, lymphoplasmacytic lymphoma and monoclonal gammopathy of undetermined significance (Li JJ, Henderson C. Cutaneous crystal storing histiocytosis: a report of two cases. J Cutan Pathol 2015; 42:136–43). In our case, a bone marrow biopsy was not performed given the lack of systemic symptoms, no significant serum paraprotein and normal imaging. The patient is currently being managed with topical clobetasol propionate 0.05% ointment and is under annual haematology surveillance with serum electrophoresis and immunoglobulins.