Umbilical Nodule in a 32-Year-Old Woman —Quiz Case

A 65-year-old woman presented with a several-day history of tender necrotic lesions on her extremities. The lesions were preceded by erythema of her right great toe that did not respond to -lactam antibiotic therapy for presumed staphylococcal paronychia. Her medical history was remarkable for aplastic anemia status post induction therapy with antithymocyte globulin, methylprednisolone, and cyclosporine. Physical examination revealed multiple erythematous, edematous nodules with central necrotic eschars on the patient’s extremities; the largest one, measuring 3.5 cm, was located on her right wrist (Figure 1). Also, there was periungual erythema with associated vesiculation on her right great toe (Figure 2). Laboratory studies at the time of evaluation were notable for a white blood cell count of 1400/μL, with an absolute neutrophil count of 700/μL (to convert values to 10/L, multiply by 0.001). A punch biopsy specimen was obtained from the lesion on the right thigh (Figure 3) for histologic evaluation and culture studies. What is your diagnosis?