Longitudinal follow-up of autoimmune neutropenia in adults-a single-cohort experience

Adult autoimmune neutropenia (AIN) is a rare and probably underrecognized immune cytopenia for which population-based adult incidence estimates are not established. Unlike the benign, self-limiting course seen in children, the adult trajectory is poorly defined. We evaluated its presentation, course, and the factors associated with the requirement for treatment.

Retrospective study of adults with neutropenia (ANC <1,500/µL) and anti-neutrophil antibodies on granulocyte immunofluorescence testing (GIFT) at a tertiary center, 2015-2025. GIFT positivity was considered supportive, not sufficient. Two patients later found to have a clonal disorder were described but excluded from outcome analyses.

A total of 41 patients were included (87.8% female; mean age 32.3 ± 14.8 years, followed 7.0 ± 7.1 years). A systemic immune disorder was present in 23 (56.1%): autoimmunity in 21 (51.2%), inborn errors of immunity in 6 (15.0%). Of 39 patients analyzed for outcome, 18 (46.2%) required neutropenia-directed therapy. These presented more often with fever (38.9% vs 4.8%, p=0.015) and thrombocytopenia (50.0% vs 14.3%, p=0.035), had lower platelet nadirs (p=0.024), and were admitted for neutropenic fever more often (3.6 vs 0.3 admissions, p=0.005). Malignancy (12.8%) and death (5.1%) occurred almost exclusively in this group, although neither difference was significant. Both nadirs were associated with the requirement for therapy (AUC 0.807).

Adult AIN is heterogeneous and frequently marks broader immune dysregulation. A substantial subgroup carries a real burden of neutropenic fever and hospitalization, identifiable at presentation by the depth of both nadirs. AIN in an adult warrants a structured immunological evaluation and risk-adapted follow-up.