Objective: To analyze the CARD15 gene in families with heritable multi-organ granulomatoses, including the original Blau syndrome kindred as well as other families with related granulomatous conditions.
Methods: Linkage mapping was performed in 10 families. Observed recombination events were used to exclude regions centromeric or telomeric to 16q12.1, and the Blau gene critical region was refined to <3 cM, corresponding to a physical distance of 3.5 megabasepairs. Based on its known biochemical function, CARD15 was analyzed as a positional candidate for the Blau syndrome susceptibility gene, by direct DNA sequencing.
Results: These studies resulted in the identification, in 5 of the families, of 2 sequence variants at position 334 of the gene product (R334W and R334Q). Affected family members from the original Blau syndrome kindred were heterozygous for the R334W missense mutation; mutations at the same position were also observed in several unrelated Blau syndrome families, some of whose phenotypes included large-vessel arteritis and cranial neuropathy. The missense mutations segregated with the disease phenotype in the families, and were not seen in 208 control alleles.
Conclusion: These findings demonstrate that CARD15 is an important susceptibility gene for Blau syndrome and for other familial granulomatoses that display phenotypic traits beyond those of classic Blau syndrome.