Granuloma annulare (GA) commonly presents as an erythematous, annular plaque with no scale. However, the subcutaneous form of GA can present as solitary or multiple deeper dermal nodules. Histopathologic examination of these lesions would demonstrate histiocytes around a focus of necrobiosis and increased mucin deposition, the intervening dermis typically appears normal. Multinucleated giant cells are frequently seen along with mild perivascular and interstitial lymphocytic infiltrate with scattered neutrophils.
Palisaded neutrophilic granulomatous dermatitis (PNGD) presents as umbilicated papules distributed symmetrically on the extremities, particularly extensor extremities, as well as on the hands and feet. PNGD is commonly associated with seropositive rheumatoid arthritis and other autoimmune diseases, including systemic lupus erythematosus. On histopathology, PNGD demonstrates a robust neutrophilic and granulomatous histiocytic infiltrate with collagen degeneration and possibly fibrin deposition. These lesions may be thought of as “rheumatoid papules,” a smaller, more superficial variant of the rheumatoid nodule.
Joseph F. Merola, MD, MMSc, is an instructor at Harvard Medical School, Brigham and Women’s Hospital, in Boston. He is board-certified in rheumatology, dermatology and internal medicine. He serves as the director of clinical trials in dermatology, co-director of the Center for Skin and Related Musculoskeletal Diseases and assistant program director for the combined medicine-dermatology residency training program.
Johanna Sheu, MS, is a medical student at Harvard Medical School. She is currently completing a research fellowship in pediatric dermatology at Boston Children’s Hospital.
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