Congenital autoimmune neutropenia in two premature neonates.

Autoimmune neutropenia (AIN) has been reported in infants and children, but not in neonates. AIN is caused by antibodies produced by the patient against their own neutrophils; therefore, it differs from the more common alloimmune neonatal neutropenia and the neonatal neutropenia because of a maternal autoimmune disease in which antineutrophil antibodies of maternal origin cross the placenta. We observed 2 cases of congenital AIN in premature neonates. These are the youngest reported cases, and indicate that AIN can have a prenatal onset. Examination of the bone marrow biopsies revealed an increase in B lymphocytes and myeloperoxidase-positive cells with a maturation arrest at the myelocyte stage. Recombinant human granulocyte colony-stimulating factor effectively treated the neutropenia, as it does in infantile AIN. Ten months after the diagnosis, 1 of the patients still requires recombinant human granulocyte colony-stimulating administration.