The KIT D816V allele burden predicts survival in patients with mastocytosis and correlates with the WHO type of the disease.

[cutaneous mastocytosis]

KIT D 816 V is present in a majority of patients with systemic mastocytosis (SM ). We determined the KIT D 816 V allele burden by quantitative real-time PCR in bone marrow and peripheral blood of 105 patients with mastocytosis . KIT D 816 V was detected in 92 /105 patients (88 %). Significant differences in the median allele burden were observed between disease subgroups : cutaneous mastocytosis (0 .042 %), indolent SM (0 .285 %), smoldering SM (5 .991 %), aggressive SM (9 .346 %), and SM with associated hematologic non-mast cell lineage disease (3 .761 %) (P < 0 .001 ). The KIT D 816 V burden also correlated with serum tryptase (R = 0 .5 , P < 0 .005 ) but not with mast cell infiltration in bone marrow or mediator symptoms . Moreover , the allele burden was of prognostic significance regarding survival (P < 0 .01 ). Patients responding to cytoreductive therapy showed a significant decrease in KIT D 816 V (P < 0 .05 ). To conclude , the KIT D 816 V burden correlates with the variant of mastocytosis , predicts survival , and is a valuable follow-up parameter in SM .