Agammaglobulinemia, X-linked 1(XLA) (BTK)
Agammaglobulinemia, X-linked 1 is an X-linked recessive disorder caused by pathogenic variants in the gene BTK. This rare primary immunodeficiency typically manifests during infancy. Most individuals with this disorder are susceptible to recurrent or persistent bacterial or enteroviral infections and are often diagnosed with pneumonia, bronchitis, otitis media, conjunctivitis, sinusitis and hepatitis. Affected individuals also present with absent or unusually small lymph nodes. Life expectancy is normal in most cases, but could be decreased depending on severity of infections. Variants in BTK can also cause an isolated growth hormone deficiency (IGHD3), which manifests early in infancy. Affected individuals have short stature due to a lack or absence of growth hormone and a weakened immune system. No clear genotype-phenotype correlation has been established.
For information about carrier frequency and residual risk, please see the residual risk table.