BTK: 22 novel and 25 recurrent mutations in European patients with X-linked agammaglobulinemia.

X linked agammaglobulinemia (XLA) is an immunodeficiency disease caused by mutations in the gene coding for Bruton's agammaglobulinemia tyrosine kinase (BTK), that is involved in signal transduction pathways regulating survival, activation, proliferation, and differentiation of B lineage lymphoid cells. XLA is a primary immunodeficiency disorder characterized by lack of mature, circulating B lymphocytes, and recurrent infections. Using Single Strand Conformation Polymorphism (SSCP) followed by direct sequencing we investigated 57 patients with XLA phenotype, with or without a positive family history, from 52 unrelated families enrolled in the Italian XLA Multicenter Clinical Study. We have identified 25 recurrent mutations, 22 novel mutations including one large deletion comprising the coding sequence from exon 11 to 18. Among the mutations identified, three were detected in different unrelated families, whereas all the others were private mutations.