Autoimmune neutropenia of infancy (AIN), the most frequent type of severe, prolonged neutropenia in young children, is often thought to be benign since serious infectious complications are less frequent than in other etiologies of severe neutropenia. The neutropenia occurs due to recognition of membrane antigens by anti-neutrophil antibodies, resulting in peripheral neutrophil destruction. The types of pathogens and foci of infections have not been elucidated in AIN cohorts.
The purpose of this study was to describe the demographics and clinical course of AIN with a focus on the incidence and type of infectious events, the pathogens involved and assessment of contributing factors.
Data was extracted from the medical records of all AIN patients treated at the tertiary Israeli referral pediatric hematology center in Schneider Children's Medical Center of Israel between 2001–2016. We focused on patient demographics, laboratory values, and physical and microbiologic descriptions of all infectious events.
A hundred and one patients diagnosed with AIN were included in the study, representing a total of 175 patient-years of follow-up, with a mean of 1.9 years per patient. Mean age at presentation was 0.8 years and at resolution 2.8 years; 90% were healthy by the age 3.8 years. At least one microbiologically proven bacterial infection was identified in 26% of the patients. Bacterial isolates were mostly gram negative, predominantly Pseudomonas species (14/34, 41% of all isolates). Pseudomonas was isolated in urinary tract infections in 6 patients, 5 cases of genital infections 2 cases of AOM and 1 skin abscess. Significant skin infections were diagnosed in thirty patients, outstandingly 25 cases of genital/ecthyma lesions occurred in 15 patients, again Pseudomonas was prevalent being the identified pathogen in 5 patients. There were only 3 episodes of bacteremia out of 559 total febrile illnesses (0.5%), notably the isolates were bacteria not covered by routine vaccinations (Kingella kingae, Sphingomonas paucimobillis, and Salmonella sp.).
AIN is considered a benign disease. Indeed, we show that the common practice of treating all febrile illnesses in AIN with broad spectrum antibiotics may be unnecessary due to the rarity of bacteremias. However, bacterial genital skin infections, caused by gram-negative bacteria especially Pseudomonas sp are common. This finding is surprising as ecthymal lesions are more commonly associated with hypoproductive neutropenias. Hence, we recommend that antibiotic therapy covering pseudomonas and other gram-negative bacteria should be prescribed to any infant with AIN and skin infection.