Hence, it is not known whether the neutropenia in ADA-deficient patients is due to an intrinsic critical role of ADA in neutrophil development or is secondary to a defect in the bone marrow stroma (18), the frequent infections and immune dysregulation that patients experience or possibly due to treatments they receive (e.g., trimethoprim-sulfamethoxazole). The gene discussed is ADA; the disease is Decreased total neutrophil count.