Treatment of chronic neutropenia of childhood responsive to cyclosporin A in vitro and in vivo.

The clinical course of a 17-year-old patient who suffered from chronic neutropenia without cyclic variation since the age of 2 is presented. The bone marrow showed absent granulopoiesis and yielded very few colony-forming units (CFU-GM) in vitro with maturation up to segmented neutrophils. Incubation with cyclosporin A (CyA) increased CFU-GM markedly. Such an increase was not found after incubation of normal bone marrow with CyA in vitro. The patient also responded to CyA in vivo and maintained adequate granulocyte counts for 7 months when she became neutropenic again. She subsequently responded to high doses of prednisolone. The clinical course and bone marrow studies suggest that the defective granulopoiesis is due to an immunologically mediated mechanism sensitive to CyA and prednisolone. Other findings in this patient, such as impaired natural killer (NK) cell activity and random and chemotactic leukocyte motility, could further point to an imbalance in the regulation of hematopoiesis. Neutropenia, NK cell defect and impaired chemotaxis may be pathogenetically connected.