A 5-year-old boy from China with a history of IgA vasculitis at 2 years of age presented with a 1-month history of progressively painful skin ulcerations on his extremities.
Two months prior, he had had an episode of nasal pustules that had not responded to antimicrobial therapy or surgical débridement, but had ultimately improved with 2 days of systemic glucocorticoid therapy.
At the current presentation, laboratory and radiographic studies showed no signs of underlying systemic disease, such as cancer, inflammatory bowel disease, or autoimmune conditions. Biopsy samples from the lesions showed a dense neutrophilic infiltrate with negative tissue cultures.
What is the diagnosis?