Rossides M, et al. - Researchers used a case-control-family study design and population-based Swedish registers to determine the familial aggregation and heritability of sarcoidosis. A total of 23,880 individuals with visits for sarcoidosis were identified in the National Patient Register using ICD codes (1964–2013). Matching of general population controls to cases (10:1) was carried out. Using the Multi-Generation Register, they selected relatives of cases and controls. The diagnosis of sarcoidosis was ascertained in the Patient Register. Conditional logistic regression and biometric models were used to determine familial relative risks (RR) for sarcoidosis and the heritability, respectively. They identified a very strong risk factor for the disease was having a relative with sarcoidosis. Although genetic variation was shown to be a partial contributing factor to the risk for sarcoidosis, still it was recognized as an important contributor.