Genomic instability on hMSH2, hMLH1, CD48 and IRF4 loci in pulmonary sarcoidosis

Pulmonary sarcoidosis shares certain features with immune disease and neoplasia, and microsatellite DNA alterations are detectable in sputum specimens of pulmonary sarcoidosis patients. The biological basis and significance of these findings remain obscure, while information regarding the genetic basis of the disease is limited. Using multiplex PCR-based microsatellite analysis, we investigated 40 markers located on 1p, 1q, 2p, 2q, 3p, 5q, 6p, 7p, 9p, 11q, 14q and 17p in 38 sputum specimens of pulmonary sarcoidosis patients. Loss of heterozygosity (LOH) was found in 13 of 38 (34.2%) patients in at least one locus. These alterations occurred in the subset of markers located in or close to DNA mismatch repair (MMR) genes, hMSH2 (2p22.3-p16.1) and hMLH1 (3p2l.32-p21.1), as well as in CD48 (1q21-q23) and IRF4 (6p23-p25), genes associated with lymphocyte activation. Microsatellite instability (MIN) was observed in five cases (13.2%) in at least one locus. Our data suggest that genomic instability in pulmonary sarcoidosis could be due to MMR defects, while alterations of lymphocyte-specific agents could account for granuloma formation.