IRAK4 and immunodeficiency disease: We previously reported an IRAK4-deficiency in a 4-year old child due to a homozygous single base substitution (C887T) in exon 8 of the IRAK4 gene that introduced a premature stop codon (Q293X) [13,14]; an identical mutation occurs in the majority of cases of IRAK4 immunodeficiency.