Immunodeficiency Associated with a Nonsense Mutation of IKBKB

We report an infant of consanguineous parents of Turkish decent with a novel immunodeficiency associated with homozygosity for a nonsense mutation of the gene encoding Inhibitor of nuclear factor kappa-B (NF-κB) kinase subunit beta (IKKβ). At five months, she presented with respiratory insufficiency and Pneumocystis jirovecii pneumonia which was successfully treated. At nine months, iatrogenic systemic infection with Mycobacterium bovis was found and eventually led to her death at age 14 months. Laboratory findings were reminiscent of hyper-IgM syndrome, but genetic testing gave no explanation before whole exome sequencing revealed a novel mutation abrogating signaling through the canonical NF-κB pathway.