Retiform Purpura Due to Microvascular Occlusion: An Archetypical Manifestation of Lucio Phenomenon in Lepromatous Leprosy

Retiform purpura is a morphological pattern that is a clinical reflection of microvascular occlusion. Although several infectious etiologies are described, leprosy remains an underrecognized cause. Lucio phenomenon is a rare vasculonecrotic reaction of untreated lepromatous leprosy, characterized by endothelial invasion by Mycobacterium leprae (M. leprae), leading to thrombosis and necrotizing vasculitic skin lesions. The present report involves a case of a 70-year-old woman who presented with purpuric and necrotic lesions over the extremities, digital discoloration, and neuritic pain, with a history of spontaneous autoamputation of digits a decade earlier. An examination revealed stellate purpura, hemorrhagic bullae, glove-and-stocking anesthesia, lagophthalmos, madarosis, and thickened peripheral nerves. Coagulation parameters were deranged, and IgM anti-β2-glycoprotein and anticardiolipin antibody test results were positive. A slit-skin smear revealed a bacteriological index of 5+. Histopathology revealed foamy histiocytes, with vasculitis, leukocytoclasia, and Fite-positive bacilli infiltrating the vessel walls. Polymerase chain reaction testing confirmed M. leprae. A diagnosis of lepromatous leprosy with microvascular occlusion secondary to the Lucio phenomenon was made. Prompt initiation of multidrug therapy and anticoagulation led to rapid recovery. Early recognition is essential to prevent irreversible tissue loss, especially in leprosy endemic countries, and is possibly an important cause of imported infectious disease in developed countries.