ClinVar

Description

The BTK c.863G>A; p.Arg288Gln variant (rs1555978277) is reported in the literature in numerous individuals with symptoms or a diagnosis of X-linked agammaglobulinemia (Abbott 2013, Conley 1998, Fiorini 2004, Futatani 2001, Lee 2010, Plebani 2002). This variant is absent from general population databases (Exome Variant Server, Genome Aggregation Database), indicating it is not a common polymorphism, and it is reported as pathogenic by multiple laboratories in ClinVar (Variation ID: 492813). The arginine at codon 288 is highly conserved, and computational analyses (SIFT, PolyPhen-2) predict that this variant is deleterious. Further, this variant occurs in the phosphotyrosine-binding pocket of a functional important SH2 domain and in vitro assays indicate that it disrupts binding to phosphorylated peptides (Tzeng 2000). Another variant at the same codon (p.Arg288Trp) has been reported in individuals with X-linked agammaglobulinemia and is considered pathogenic (Fiorini 2004, Plebani 2002, Tzeng 2000). Based on available information, the p.Arg288Gln variant is considered to be pathogenic. References: Abbott JK et al. Coding-region alterations in BTK do not universally cause X-linked agammaglobulinemia. J Allergy Clin Immunol. 2013 Nov;132(5):1246-8. Conley ME et al. Mutations in btk in patients with presumed X-linked agammaglobulinemia. Am J Hum Genet. 1998 May;62(5):1034-43. Fiorini M et al. BTK: 22 novel and 25 recurrent mutations in European patients with X-linked agammaglobulinemia. Hum Mutat. 2004 Mar;23(3):286. Futatani T et al. Bruton's tyrosine kinase is present in normal platelets and its absence identifies patients with X-linked agammaglobulinaemia and carrier females. Br J Haematol. 2001 Jul;114(1):141-9. Lee PP et al. Clinical characteristics and genotype-phenotype correlation in 62 patients with X-linked agammaglobulinemia. J Clin Immunol. 2010 Jan;30(1):121-31. Plebani A et al. Clinical, immunological, and molecular analysis in a large cohort of patients with X-linked agammaglobulinemia: an Italian multicenter study. Clin Immunol. 2002 Sep;104(3):221-30. Tzeng SR et al. Stability and peptide binding specificity of Btk SH2 domain: molecular basis for X-linked agammaglobulinemia. Protein Sci. 2000 Dec;9(12):2377-85.