Pb2058: screening for antineutrophil antibodies in patients with severe chronic neutropenia at alexandria university children’s hospital

Topic: 12. Bone marrow failure syndromes incl. PNH - Clinical Background: Neutropenia is defined as an absolute neutrophil count (ANC) <1.5 ×109/L. Neutropenia is considered “severe” when the ANC is < 0.5 ×109/L and “chronic” when it lasts longer than 3 months. There are several causes of isolated severe chronic neutropenia (SCN), including congenital and acquired causes like autoimmune neutropenia (AIN). Aims: To screen for antineutrophil antibodies in children with SCN in our center. Methods: This cross-sectional study included all SCN patients who were following at the hematology clinic of Alexandria University Children’s Hospital, Alexandria, Egypt. The demographic, initial clinical, and laboratory data were collected. We tested for antineutrophil antibodies using the LABscreenTM Multi kits (Thermo Fischer) using a Luminex technique to detect the presence of human neutrophil antibodies (HNA) specific antibodies in patient’s serum. Results: A total of 27 patients were included; sixteen (59.3%) patients were males. The patients’ age ranged from 11 to 218 months, and the mean age at the onset of neutropenia was 21.1 months. The majority of patients (n=26, 96.3%) presented with an infection, with a median ANC of 0.7 ×109/L and a median absolute monocytic count of 0.4 ×109/L. Overall, at least one antineutrophil antibody was detected in 17 patients (63%) of individuals. The most prevalent antibodies were against HNA-1a (n=7), and HNA-1c (n=5), while the least prevalent were HNA-a2 and HNA-4a (each in only one patient). The diagnosis of congenital neutropenia was confirmed in 8 patients (either severe congenital neutropenia or cyclic neutropenia), of whom 5 had at least one detectable antibody (62.5%), while 12 out of 19 patients with no evidence of congenital neutropenia had at least one detectable antibody (52%). Summary/Conclusion: Antineutrophil antibody detection was common among children with SCN and was not specific to patients suspected to have immune/idiopathic neutropenia, as it was also found in patients with proven congenital neutropenia. Detecting antineutrophil antibodies may not be enough to exclude a diagnosis of congenital neutropenia. Repeating the test over time and using different techniques of measuring antineutrophil antibodies may be warranted to confirm the diagnosis of autoimmune neutropenia in suspected patients. Keywords: Neutropenia, Anti-neutrophil antibody, Severe congenital neutropenia, Severe chronic neutropenia