Decreased total neutrophil count Autoimmune neutropenia SNOMEDCT_US:234425008 Neutropenia in presence of anti-neutropil antibodies HP:0001904 Abnormal decrease of the absolute number of neutrophils in the blood, per microlitre, compared to a reference range for a given sex and age-group, accompanied by the detection of anti-neutrophil antibodies. The antibodies are directed against the cell surface membrane and have no relationship with antineutrophil cytoplasmic antibodies (ANCAs) in the vast majority of cases. It is important to highlight that there are frequent difficulties in the detection of autoantibodies causing AIN due to the labile nature of granulocytes (not storable without activation and consequent autolysis). This type of neutropenia is commonly seen with autoimmune neutropenia of infancy (AIN), also called primary autoimmune neutropenia, is a disease in which antibodies recognize membrane antigens of neutrophils, mostly located on immunoglobulin G (IgG) Fc receptor type 3b (Fc-gamma-IIIb receptor), causing their peripheral destruction. UMLS:C0340971 Autoimmunity