... Approximately one-third of all mutations in the BTK gene are missense and some of these reduce the stability of the protein.This is exemplified by mutations in the BTK motif of the Tec homology (TH) ... ancient and constitutes the second largest family of cyto-plasmic tyrosine kinases. In 1993, loss -of- function mutations in the BTKgene were reported as the cause of X-linked agammaglobulinemia. Of ... loss -of- function of BTK and ITK and the gain -of- function fusions ITK–SYK and BTK–SYKAlamdar Hussain1,2,*, Liang Yu1,3,*, Rani Faryal1,2, Dara K. Mohammad1, Abdalla J. Mohamed1,4 and C. I....