However, patients with mastocytosis and HαT appear to present with features of lower mast cell burden, such as lower KIT D816 V variant allele frequency (VAF) in blood, bone marrow (BM) aspirates or BM biopsies, lower BM cell infiltration, and fewer BM MC clusters, even within subgroups of SM (18, 19, 23). Here, KIT is linked to mastocytosis.