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A woman in her 30s presented with a chronic history of slowly expanding asymptomatic papules on the dorsal hands since childhood, with more recent involvement of both forearms. She denied photosensitivity, arthritis, or muscle weakness. Examination revealed multiple discrete reddish-brown, well-defined, smooth 2- to 6-mm dome-shaped papules (Figure, A). There were no nail changes or mucous membrane involvement.
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B. Progressive mucinous histiocytosis
Histopathologic evaluation revealed a CD163- and CD68PG-positive diffuse dermal histiocytic infiltrate with scattered mast cells and abundant mucin. Results of S-100 protein and CD1a stains were negative. Electron microscopy showed concentric electron dense lamellar inclusion bodies in the cytoplasm of histiocytes. There was no clinical improvement in symptoms when treated with class I topical or intralesional corticosteroids.
Progressive mucinous histiocytosis (PMH) is a rare, benign non–Langerhans cell histiocytosis of the skin that presents as few to numerous variably sized, skin-colored to reddish-brown papules on the dorsal hands, extensor forearms, face, or legs, slowly progressing without spontaneous resolution.1,2 There is no mucosal or visceral involvement, systemic symptoms, or laboratory abnormalities.2 Both hereditary and sporadic forms exist, with the former typically presenting in childhood and the latter in adulthood.1,2 Women are preferentially affected.1- 3 Histopathology shows a dermal accumulation of epithelioid or spindle-shaped histiocytes with prominent dermal mucinosis.2 Variable numbers of mast cells and hemosiderosis are also commonly present.2 The infiltrate is positive for CD68 and CD163 and negative for CD1A, S-100, and Langerin.2
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Corresponding Author: Jason C. Sluzevich, MD, Department of Dermatology, Mayo Clinic, 4500 San Pablo Rd, Jacksonville, FL 32224 (firstname.lastname@example.org).
Published Online: March 17, 2021. doi:10.1001/jamadermatol.2021.0188
Conflict of Interest Disclosures: None reported.
Additional Contributions: We thank the patient for granting permission to publish this information.
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