Cladribine Plus Pegylated Interpheron Alfa-2a in Systemic Mastocytosis

Inclusion Criteria: * Age older than 18 years. * Diagnosis of advanced systemic mastocytosis (aggressive systemic mastocytosis or proggressing systemic mastocytosis) with D816V or other exon 17 KIT mutations. * ECOG ≤ 3. * Signed informed consent. Exclusion Criteria: * Impaired liver function (total bilirubin ≥ 2.0 mg/dl, AST or ALT \> 3 x upper limit of normal)not related to mastocytosis. * Impaired renal function (≥ 2.0 mg/dL)not related to mastocytosis. * Grade III-IV cytopenias not related to mastocytosis. Severe cardiopathy (grade III/IV of NYHA, or left ventricular ejection fraction \< 50%). * Pregnancy or breastfeeding. * Female patients who do not use contraceptive methods.