KIT (KIT proto-oncogene, receptor tyrosine kinase) is a gene that encodes a receptor tyrosine kinase involved in proliferation of mast cells, melanocytes, germ cells, and hematopoietic stem cells. The KIT D816V mutation is a specific genetic alteration found in patients with systemic mastocytosis, a rare disorder characterized by the abnormal accumulation of a white blood cell type called mast cells in various tissues of the body. This is a somatic point mutation occurring in the exon 17 of KIT gene that replaces amino acid aspartate with the amino acid valine at position 816 in the protein. This conformational change results in ligand-independent constitutive activation of KIT and leads to increased cell proliferation and accumulation in various organs, and a reduction in cell death.

Determining the presence of the KIT D816V mutation is crucial for confirming the diagnosis, guiding treatment decisions, and assessing the prognosis for patients with systemic mastocytosis. Tyrosine kinase inhibitors, such as imatinib, which specifically target the abnormal KIT signaling pathway may be used as a treatment for systemic mastocytosis patients carrying the D816V mutation.