102 Patients with Primary Autoimmune Neutropenia : An Analysis of the European Severe Chronic Neutropenia International Registry (SCNIR)

Abstract

Background: Primary Autoimmune Neutropenia (AIN) is the most frequent type of neutropenia in children with a prevalence of 1/100,000 between infancy and 10 years of age. Primary AIN is caused by anti-neutrophil antibodies binding to neutrophil-specific antigens, resulting in a decrease of circulating neutrophils in the blood, but normal numbers of mature neutrophils in the bone marrow. Typically, primary AIN is present from infancy on until spontaneous remission in early childhood, when anti-neutrophil antibodies disappear. Patients with primary AIN show severe to moderate neutropenia but only rarely suffer from serious infections. Patients remain in the registry for follow up after normalization of blood counts to evaluate late secondary events. Aims: Here we describe the cohort of AIN pts with positive anti-neutrophil antibody testing documented by the European Branch of the SCNIR. We analyzed the course of neutropenia, the frequency of G-CSF treatment for AIN, the incidence of severe bacterial infections and administration of AB prophylaxis. Methods: We identified 102 primary AIN patients within the neutropenia cohort documented by the European Branch of the SCNIR since 1994. We classified primary AIN by positive anti-neutrophil antibody testing (95 pts) or severe neutropenia in peripheral blood with normal bone marrow morphology in patients with age under 5 years (7 pts). Results: Primary AIN has been identified in 102 (61 female; 41 male) pts. The median age of the cohort is 5.18 years (range 1.37-22.71 years), with 630.28 pt years under observation. Median age at diagnosis was 12.07 months (range 0.9-70 months). All pts are currently alive, 40 patients already resolved from primary AIN at a median age of 3.02 years (range 0.83-9.08 years). Median follow-up time after neutropenia had resolved was 2.25 years (range 0-9.27 years). Sixteen of 102 pts (15.7%) received intermittent G-CSF treatment with a median dose of 4.5 µg/kg/day compared to 4.77 µg/kg/day for the congenital neutropenia cohort of the SCNIR Europe. Analysis of infections (tab.1) showed less minor and severe infections comparing to congenital neutropenia (CN) pts. Life-threatening infections like liver abscesses were not seen in primary AIN patients but in 1.8% of CN pts. Twelve AIN pts (11.7%) have received antibiotic prophylaxis for prevention of infection, 6 pts intermittent and 6 pts continuously. However, antibiotic prophylaxis was usually stopped before termination of AIN. Due to the milder course of infections most AIN pts were able to go to Kindergarten and to live a normal life. In 3 pts additional auto-immune related diseases were identified (autoimmune thrombocytopenia, allergic colitis and Kawasaki syndrome) during AIN. Sixteen of 102 AIN patients received genetic analysis, with no mutation being detected. In addition to the 102 AIN pts we identified another 31 CN pts who have initially been classified as AIN due to positive anti-neutrophil antibodies, but who were later genetically confirmed as CN (15 ELANE+, 8 HAX1+, 2 SBDS+, 2 CXCR4+, 2 CSF3R+, 1 G6PC3+). This proportion of pts showed more and more severe infections compared to primary AIN. Genetic testing has been performed in these pts due to ongoing infections and prolonged neutropenia until school age. Conclusions: Pts suffering from primary AIN present with severe to moderate neutropenia. A minority of pts might require G-CSF treatment on demand/interventionally due to antibiotic resistant infections, but long-term G-CSF treatment is regularly not indicated. Primary AIN is a self-limiting condition and in most pts neutropenia resolves until early childhood. Accumulation of secondary diagnoses like autoimmune related diseases, though postulated, has not been confirmed for AIN pts by our data. In AIN pts with severe infections, or prolonged neutropenia CN should be ruled out by genetic analysis and/or bone marrow morphology. Registries are needed to document long-term data on primary AIN pts to analyse potential additional features of primary AIN, possibly other accompanying autoimmune diseases. Disclosures No relevant conflicts of interest to declare.

Autoimmune neutropenia associated with influenza virus infection in childhood: a case report

“…Autoimmune neutropenia is a benign disease typically presenting in infants or toddlers. In a large series of 240 children with autoimmune neutropenia the median age of onset was 8 months, all of them presenting before 3 years of age [ 6 ], although the presentation may be beyond that age in early childhood [ 7 ]. The course is variable, with spontaneous resolution in most cases that may last several months or years.…”

“…The course is variable, with spontaneous resolution in most cases that may last several months or years. In two large series the median times of resolution were 17 months and 3 years, respectively [ 6 , 7 ]. Although sometimes a genetic panel to detect the mutation of common genes associated with congenital neutropenia is performed [ 8 ], it is not usually necessary when there is a high suspicion of autoimmune neutropenia [ 7 ]…”

“…The course is variable, with spontaneous resolution in most cases that may last several months or years. In two large series the median times of resolution were 17 months and 3 years, respectively [6,7]. Although sometimes a genetic panel to detect the mutation of common genes associated with congenital neutropenia is performed [8], it is not usually necessary when there is a high suspicion of autoimmune neutropenia [7] Children with autoimmune neutropenia rarely suffer from serious infections, since circulating neutrophils, although low in number, are normally functional, and therefore capable of defending the host against such infections.…”