- Solitary or, more commonly, multiple, soft, elevated, and well-circumscribed papules, plaques, or nodules are observed.
- Lesions are most commonly located over the face. Reported extrafacial locations include the scalp, the trunk, and the upper and lower extremities.
- The size of the lesions varies from a few millimeters to several centimeters in diameter.
- The color varies from shades of dull red to brown, blue, and purple.
- Lesions have a smooth surface with prominent follicular orifices (peau d'orange) and may be covered by telangiectases.
Copyright : Mitsuhiro Sugiura, M.D.
- The epidermis is unaffected.
- A grenz zone of uninvolved dermis is located beneath the epidermis. Below the grenz zone is a dense, polymorphous inflammatory infiltrate located most often in the papillary and mid dermis.
- The infiltrate consists of neutrophils, lymphocytes, eosinophils, monocytes, and, occasionally, mast cells.
- Vasculitic changes, including perivascular inflammation with nuclear dust and vessel wall damage, are often observed.
- Extravasated RBCs and hemosiderin deposition are found, which may contribute to the color of the lesions.
- Later, lesions may show considerable fibrosis around venules.
- Direct immunofluorescence reveals immunoglobulin G, fibrin, and, occasionally, immunoglobulin M deposition at the basement membrane zone and perivascularly.
- Electron microscopy reveals more perivascular eosinophils than suggested by light microscopy. Charcot-Leyden crystals, the eosinophil granules, are evident within eosinophils as well as histiocytes, providing evidence of degranulation.
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