Retiform purpura in plaques: a morphological approach to diagnosis.

Retiform purpura (RPP) is a livedoid pattern of cutaneous haemorrhage that may result from vasculitis, occlusion or altered coagulation. When this pattern presents as palpable plaques, vascular inflammation is present, and the differential diagnosis includes calciphylaxis, warfarin-induced skin necrosis, antiphospholipid antibody syndrome and heparin-induced skin necrosis. These diseases are clinically aggressive and may result in significant morbidity and mortality. Early recognition is essential to make the necessary medication changes and to begin intervention. Our morphological approach to diagnosis differs from traditional methods and can expedite management. Biopsy results and laboratory findings are then used to verify the diagnosis and determine the specific cause. This approach may allow the development of a treatment plan prior to availability of all ancillary data. Clinical and histological cases are presented for these four syndromes presenting as RPP.