Blau syndrome and related genetic disorders causing childhood arthritis.

Blau Syndrome (BS) is an inheritable disorder characterized by granulomatous polyarthritis, panuveitis, and exanthema. It was described by Edward Blau in 1985, the same year in which Douglas Jabs reported a very similar family. Clinically indistinguishable from early onset sarcoidosis (EOS), both are now known to share a mutated form of caspase recruitment domain-15 (CARD 15), a protein involved in activation of nuclear factor kappa B which is in turn an up-regulator of pro-inflammatory cytokine transcription. An association between BS and EOS was suspected for years given the striking similarities of the core triad (arthritis-uveitis-dermatitis) and a common emerging pattern of systemic involvement. Hence, the familial form (BS) and the sporadic form (EOS) are almost certainly the same illness/defect, inherited in the first and acquired in the second as a result in most cases of a de novo mutation. Another form of granulomatous arthritis with uveitis, Crohn's disease, has also been associated with mutations in CARD 15 (albeit at a different domain) and despite similar phenotypes there are obvious differences including gut inflammation and pyoderma gangrenosum in Crohn's disease. This paper will review the clinical characteristics of these three disorders and their association with mutations in the CARD 15 gene.