KEL (Kell Metallo-Endopeptidase (Kell Blood Group)) is a Protein Coding gene. This gene encodes a type II transmembrane glycoprotein that is the highly polymorphic Kell blood group antigen. It presents two major alleles, KEL1(K) and KEL2(k), but a variety of mutations give rise to weakened (K(mod) phenotype) or lack (K0 phenotype) of Kell antigen expression. The Kell system, encoded by the KEL gene, is one of the most clinically important blood group systems. The very rare KEL:5 results from silent KEL genes also called KELnull alleles. In a few cases, the rare KEL:1,-2 phenotype may be associated with silent KEL*02 alleles. Diseases associated with KEL include Blood Group--Kell System and Choreoacanthocytosis.