Isolated foot ulcer complicating acute leukemia: an unusual manifestation of herpes simplex virus infection simulating pyoderma gangrenosum.

An isolated foot ulcer developed in a child with newly diagnosed acute mixed lineage leukemia during induction chemotherapy. Despite its clinical resemblance to pyoderma gangrenosum, herpes simplex virus infection was eventually diagnosed on histopathology. Treatment with oral acyclovir was ineffective, but the ulcer healed with intravenous acyclovir followed by oral valaciclovir. Viral infection remains an unusual but important cause of isolated extragenital cutaneous ulceration in the immunocompromised child.