We report the case of a 10-month-old girl who presented with a spontaneous ulcer on the left buttock which failed to heal despite antibiotic therapy. Histology showed changes consistent with pyoderma gangrenosum and the ulcer resolved rapidly with super-potent topical steroids under occlusion. Blood tests revealed a persistent neutropenia. Immunoglobulin G (IgG) antineutrophil antibodies were detected in the serum, directed against human neutrophil antigen (HNA)-1a. Bone marrow studies showed normocellular marrow with no evidence of dysplasia. T and B cell subsets and karyotype analysis were normal. Autoimmune neutropenia is an uncommon self-limiting condition in young children. Pyoderma gangrenosum is rare in infants, although the buttocks are a common site of involvement in this age group. Pyoderma gangrenosum in infancy can be associated with systemic disease as in adults, particularly myelodysplasia and leukemia, arthritis and inflammatory bowel disease. However, the association of pyoderma gangrenosum and autoimmune neutropenia of infancy has not previously been reported.