The KIT D 816 V allele burden predicts survival in patients with mastocytosis and correlates with the WHO type of the disease

KIT D816V is present in a majority of patients with systemic mastocytosis ( SM ). We determined the KIT D816V allele burden by quantitative real‐time PCR in bone marrow and peripheral blood of 105 patients with mastocytosis. KIT D816V 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 D816V 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 D816V ( P  <   0.05). To conclude, the KIT D816V burden correlates with the variant of mastocytosis, predicts survival, and is a valuable follow‐up parameter in SM .