Background: A genetic predisposition to sarcoidosis has long been postulated, although no specific susceptibility genes are known. Candidate genes for the two granulomatous inflammatory disorders with clinical similarities to sarcoidosis, Blau syndrome and Crohn's disease, have been localized to a 40 centimorgan region spanning the chromosome 16 centromere.
Patients and methods: Using a sample of 35 African-American sibling pairs, who both had clinically confirmed sarcoidosis, we tested for genetic linkage between the 16p12-q21 interval (the likely location of the Blau syndrome gene) and sarcoidosis.
Results: We found no evidence for linkage to any of the eight markers we tested in the 16p12-q21 interval. Ninety percent of the 16p12-q21 region had a LOD score < -2 for a dominant gene conferring a relative risk of 3 or greater for sarcoidosis. One hundred percent of the region had a LOD score < -2 for a dominant gene with a relative risk of 3.5 or greater or recessive gene with relative risk of 2.5 or greater. Based on simulation results we could not exclude a dominant gene with relative risk < 5 at the 0.05 significance level, nor a recessive gene with relative risk < 3, over the entire 16p12-q21 interval.
Conclusions: While the clinical similarities between Blau Syndrome and sarcoidosis suggest genetic homogeneity between the disorders, we found no evidence for linkage of sarcoidosis to the Blau syndrome locus. Our exclusion results suggest that the Blau Syndrome gene does not have a major effect on sarcoidosis susceptibility.