Transient autoimmune neutropenia due to anti-NA1 antibody.

A 6-month-old girl developed severe, but transient neutropenia due to an antibody against a neutrophil-specific antigen, NA1. The mean absolute neutrophil count was 380/microliter for 2 months and spontaneously returned to normal as the anti-NA1 antibody disappeared. After recovery, the NA1 antigen was demonstrated on the patient's neutrophils. No etiology was found. There was no therapy directed at suppressing the antibody or increasing the neutrophil count. Life-threatening infection did not occur during the neutropenia.