A) Small vessel vasculitis
PPD is often confused with small vessel vasculitis, particularly leukocytoclastic vasculitis (LCV). Both vasculitis and PPD have a predilection for dependent areas such as the legs and buttocks. The golden-brown pigmentation and presence of minute petechiae in PPD, rather than larger purpuric lesions, helps to distinguish these entities. Leukocytoclastic vasculitis is commonly associated with drugs, infection, or an underlying autoimmune disease, whereas PPD often occurs as an isolated finding. A biopsy of LCV would demonstrate vessel wall destruction and fibrin deposition, which are features that are absent in cases of PPD.
Dr. Femia completed a fellowship in dermatology–rheumatology at Brigham and Women’s Hospital in Boston, MA, and is now an assistant professor in the department of dermatology at New York University. She is a diplomat of the American Board of Dermatology.
Dr. Merola is an instructor in the department of dermatology at Harvard Medical School and an instructor in the department of medicine, division of rheumatology at Brigham and Women’s Hospital, both in Boston. He is the assistant program director for the combined medicine–dermatology training program and a diplomat of the American Board of Dermatology and the American Board of Internal Medicine.