Interferon alpha and systemic mastocytosis. Analysis of therapeutic efficacy in 6 cases

OBJECTIVE: To report the results obtained with the application of alpha-IFN for the treatment of a small group of patients diagnosed of systemic mastocytosis (SM) in the setting of a general hospital. PATIENTS AND METHODS: Six patients out of a group of 14 with the diagnosis of MS were prospectively selected from January 1991 to December 1996. Two patients had aggressive variant with lymph node involvement and eosinophilia and the other four had severe and repeated crises through release of mediators not controlled under symptomatic therapy. All patients received alpha-2b-IFN with gradual doses until a mean dose of 9 MU/week was obtained, associated with anti-H1 and anti-H2 antithistaminic agents and ketotiphen. Monthly clinical and analytical studies were performed until stabilization of the clinical picture and histamine metabolite measurements in urine every 6 months and histologic evolution of bone marrow every 12 months. RESULTS: Mean age at diagnosis was 41 years (range: 26-28), M/F ratio 3/3, mean evolution time 50.5 months and mean time under therapy with alpha-IFN 15.6 months (range: 3-26). Six months after therapy was initiated a decrease in the frequency and severity of crises through release of mediators and a slight improvement in cutaneous lesions, resolution of liver enlargement and ascites were observed. Treatment tolerance was quite acceptable and dose reduction was required in only two cases. Bone marrow assessment at one year showed a similar involvement, with decrease in the number of paratrabecullar nodules. CONCLUSIONS: The efficacy of alpha-2b-IFN therapy in SM is not clearly established, although the results obtained in this study seem encouraging. To obtain valid conclusions, a larger number of patients with similar characteristics and a longer follow-up with uniform assessment criteria are required.