Osteomyelitis of the ischium: unusual presentation.

A 7-year-old boy presented with urinary symptoms and umbilical discharge. A perivesical abscess was drained from which Staphylococcus aureus was cultured. He responded to antibiotics. Subsequently, he developed a discharging sinus in the gluteal region. A plain radiograph, which had previously been normal, confirmed osteomyelitis of the ischial bone.