A novel mutation in the JH4 domain of JAK3 causing severe combined immunodeficiency complicated by vertebral osteomyelitis

JAK3 is a tyrosine kinase essential for signaling downstream of the common gamma chain subunit shared by multiple cytokine receptors. JAK3 deficiency results in T⁻ B⁺ NK⁻ severe combined immune deficiency (SCID). We report a patient with SCID due to a novel mutation in the JAK3 JH4 domain. The function of the JH4 domain remains unknown. This is the first report of a missense mutation in the JAK3 JH4 domain, thereby demonstrating the importance of the JH4 domain of JAK3 in host immunity.