Severe chronic neutropenia: pathophysiology and therapy.

The development of recombinant-met human granulocyte-colony stimulating factor (r-metHuG-CSF) for clinical use has had a major influence on the treatment of many diseases. This impact has perhaps been greatest for treatment of severe chronic neutropenia (SCN) conditions for which there were no predictably effective treatment before the availability of these growth factors, particularly r-metHuG-CSF (Filgrastim, Amgen Inc, Thousand Oaks, CA; or Lenograstim, Rhone-Poulenc Rorer, Milan, Italy). Based on careful studies in many countries it is now known that more than 95% of these patients will respond promptly to r-metHuG-CSF treatment with normalization of the blood neutrophil levels and reduction in the occurrence of both major and minor consequences of their severe neutropenia. The availability of this treatment will undoubtedly lead to much additional research on the mechanisms governing neutrophil production and the basic mechanisms that can cause neutropenia among patients who have SCN. Among patients who have SCN those who are diagnosed to have severe congenital neutropenia (Kostmann's syndrome) or Shwachman-Diamond syndrome are at risk of developing myelodysplasia and/or acute myelogenous leukemia. The role of r-metHuG-CSF in facilitating the risk remains to be determined. Thus, it is important that long-term evaluation of the safety and efficacy of treatment of SCN and cooperation in research on these rare conditions proceed under the auspices of an international registry monitoring the clinical outcome of patients with severe congenital neutropenia.