A large cohort from an immunology reference center and an algorithm for the follow-up of chronic neutropenia.

Chronic neutropenia causes involve nutritional deficiencies and inborn errors of immunity(IEI), such as severe congenital neutropenia. To classify common chronic neutropenia causes in a pediatric immunology unit. We enrolled 109 chronic neutropenia patients admitted to a pediatric immunology department between 2002-2022. We recorded clinical/laboratory features and genetic characteristics. The male/female ratio was 63/46. Fifty-eight patients had parental consanguinity(57.4%). 26.6% (n = 29) patients had at least one individual in their family with neutropenia. Common symtpoms at presentation were upper respiratory tract infections(URTI)(31.1%), oral aphthae(23.6%), skin infections(23.6%), pneumonia(20.8%), and recurrent abscesses(12.3%). Common infections during follow-up were URTI(56.8%), pneumonia(33%), skin infections(25.6%), gastroenteritis(18.3%), and recurrent abscesses(14,6%). Common long-term complications were dental problems(n = 51), osteoporosis(n = 22), growth retardation(n = 14), malignancy(n = 16)[myelodysplastic syndrome(n = 10), large granulocytic leukemia(n = 1), acute lymphoblastic leukemia(n = 1), Hodgkin lymphoma(n = 1), EBV-related lymphoma(n = 1), leiomyosarcoma(n = 1), and thyroid neoplasm(n = 1)]. We performed a genetic study in 86 patients, and 69(71%) got a genetic diagnosis. Common gene defects were HAX-1(n = 26), ELA-2 (ELANE)(n = 10), AP3B1(n = 4), and ADA-2(n = 4) gene defects. The IEI ratio(70.6%) was high. GCSF treatment(93.4%), immunoglobulin replacement therapy(18.7%), and HSCT(15.9%) were the treatment options. The mortality rate was 12.9%(n = 14). The most common long term complications were dental problems that is three times more common in patients with known genetic mutations. We prepared an algorithm for chronic neutropenia depending on the present cohort. An important rate of inborn errors of immunity, especially combined immunodeficiency(11.9%) was presented in addition to congenital phagocytic cell defects. Early diagnosis will allow us tailor the disease-specific treatment options sooner, preventing irreversible consequences.