|Other names: Arthrocutaneouveal granulomatosis|
|Coarse facial features in a boy with Blau syndrome|
Blau Syndrome is an autosomal dominant genetic inflammatory disorder which affects the skin, eyes, and joints. It is caused by a mutation in the NOD2 (CARD15) gene. Symptoms usually begin before the age of 4, and the disease manifests as early onset cutaneous sarcoidosis, granulomatous arthritis, and uveitis.
Symptoms and signs
The clinical presentation of this condition is consistent with the following:
- Patchy darkened skin
- Joint swelling
- Corneal inflammation
- Decreased joint mobility
- Posterior uveitis
- Skin rash
The elucidation that the gene defect in BS involves the CARD15/NOD2 gene has stimulated many investigators, to define how this gene operates as part of the innate immune system, that responds to bacterial polysaccharides, such as muramyl dipeptide, to induce signaling pathways that induce cytokine responses, and protect the organism. In BS the genetic defect seems to lead to over expression, and poor control of the inflammatory response leading to widespread granulomatous, inflammation and tissue damage.
The evaluation of Blau syndrome is done via determining the presence of noncaseating granulomatous inflammation, synovial/conjunctival biopsy, and genetic testing 
Treatment has included the usual anti inflammatory drugs such as adrenal glucocorticoids, anti-metabolites and also biological agents such as anti-TNF and infliximab all with varying degrees of success.
In 1985 Edward Blau, a pediatrician in Marshfield, Wisconsin, reported a family that over four generations had granulomatous inflammation of the skin, eyes and joints. The condition was transmitted as an autosomal dominant trait. In the same year Jabs et al. reported a family that over two generations had granulomatous synovitis, uveitis and cranial neuropathies. The condition was transmitted in an autosomal dominant fashion. In 1981 Malleson et al. reported a family that had autosomal dominant synovitis, camptodactyly, and iridocyclitis. One member died of granulomatous arteritis of the heart and aorta. In 1982 Rotenstein reported a family with granulomatous arteritis, rash, iritis, and arthritis transmitted as an autosomal dominant trait over three generations. Then in 1990 Pastores et al. reported a kindred with a phenotype very similar to what Blau described and suggested that the condition be called Blau Syndrome (BS). They also pointed out the similarities in the families noted above to BS but also pointed out the significant differences in the phenotypes.
In 1996 Tromp et al. conducted a genome wide search using affected and non affected members of the original family. A marker, D16S298, gave a maximum LOD score of 3.75 and put the BS susceptibility locus within the 16p12-q21 interval. Hugot et al. found a susceptibility locus for Crohn disease, a granulomatous inflammation of the bowel, on chromosome 16 close to the locus for BS. Based on the above information Blau suggested in 1998 that the genetic defect in BS and Crohn Disease might be the same or similar.
Finally in 2001 Miceli-Richard et al. found the defect in BS to be in the nucleotide-binding domain of CARD15/NOD2. They commented in their article that mutations in CARD15 had also been found in Crohn's disease. Confirmation of the defect in BS being in the CARD15 gene was made by Wang et al. in 2002 using the BS family and others. With that information the diagnosis of BS was not only determined by phenotype but now by genotype.
Early onset sarcoidosis is BS without a family history, BS has been diagnosed in patients who have not only the classic triad but granuloma in multiple organs.
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