Antineutrophil cytoplasmic autoantibody specific for proteinase 3 in a patient with shunt nephritis induced by Gemella morbillorum.

A 17-year-old girl had been placed with ventriculoperitoneal, then ventriculoatrial shunts for congenital hydrocephalus since birth. The patient originally was diagnosed as having a lupus-like disease, but later turned out to have shunt nephritis, presenting with fever, proteinuria, pancytopenia, and hypocomplementemia. Antineutrophil cytoplasmic autoantibody specific for proteinase 3 (PR3-ANCA) was detected in her serum. The patient received oral prednisolone and repeated methylprednisolone pulses, with essentially no beneficial effects. A gram-positive coccus, Gemella morbillorum, was recovered from her blood as well as cerebrospinal fluid, and the culture of the shunt catheter established the diagnosis of shunt nephritis. Removal of the shunt catheter improved symptoms dramatically and decreased PR3-ANCA in serum to an undetectable level. Because steroids had no effects and the control of bacterial infection lowered PR3-ANCA levels, the antibody would have been induced by continuous infection with G morbillorum.