Diagnosis and Clinical Course of Autoimmune Neutropenia in Infancy: Analysis of 240 Cases

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Abstract
Primary autoimmune neutropenia (AIN) is caused by granulocyte-specific autoantibodies and occurs predominantly in infancy. Clinical presentation and diagnosis have not been well established, resulting in burdening diagnostic investigations and unnecessary treatment with granulocyte colony-stimulating factor (G-CSF). In the present study, clinical, laboratory, and immunologic data of 240 infants with primary AIN were evaluated. Suspected association with parvovirus B19 infection was investigated using serologic and DNA-based methods. Primary AIN was mainly diagnosed at the age of 5 to 15 months but was observed as early as day 33 of life. In 90% of the cases, AIN was associated with benign infections despite severe neutropenia. Spontaneous remission, shown by 95% of the patients, usually occurred within 7 to 24 months. Autoantibodies in the patient's sera were not always present, and screening had to be repeated several times until antibody detection succeeded. About 35% of the autoantibodies showed preferential binding to granulocytes from NA1 and NA2 homozygous donors. Bone marrow was typically normocellular or hypercellular, with a variably diminished number of segmented granulocytes. A significant association with parvovirus B19 infection was not found. Symptomatic treatment with antibiotics was sufficient in most patients. Eighty-nine percent of the patients received antibiotics (cotrimoxazole) for prophylaxis of infections. For severe infections or for surgical preparation, G-CSF, corticosteroids, and intravenous IgG were administered, resulting in increased neutrophil counts in 100%, 75%, and 50% of the patients treated, respectively. In combination with the detection of granulocyte-specific antibodies, the typical clinical picture allowed diagnosis of AIN without burdening investigations. Treatment with G-CSF was found to be a reliable alternative to temporarily increase the neutrophil count.