Severe chronic neutropenia

A neutropenia characterized by persistent absolute neutrophil count below 0.5 x 10^9/L lasting for at least 3 months, not explained by medication use, infection or another underlying condition, and associated with recurrent and potentially life-threatening bacterial infections. The major clinical subtypes include congenital, cyclic, idiopathic, and autoimmune neutropenia, which share common diagnostic evaluation, treatment strategies, and long-term follow-up.