Sarcoidosis: Family history is a very strong risk factor – 39% of disease risk due to genetics

What is it about?

Sarcoidosis is a relatively rare disease where granulomatous inflammation infiltrates the lungs and adjacent lymph nodes in most patients. The disease can potentially affect any organ or system with severe consequences. The etiology of sarcoidosis is unknown, but it is thought to be triggered by an unidentified environmental factor in a genetically susceptible individual. In this study, we used Swedish registers to identify individuals with the disease, general population controls without the disease, and their relatives. We estimated the risk of developing sarcoidosis when having relatives diagnosed with the disease and the relative contribution of genetic and environmental factors in disease occurrence. We have shown that having a first degree relative* with the disease increases the risk for developing the disease by almost 4-fold. The relative risk is higher when having two or more first degree relatives with the disease and lower when having a half-sibling** with the disease. We have found no differences between male and female patients. In our data, 39% of the susceptibility to sarcoidosis could be explained by genetic variation in the population, and the remaining 61% by non-shared (among individuals who were reared together) environmental factors. * You and a first degree relative share 50% of your genetic makeup. ** You and a half-sibling share 25% of your genetic makeup.

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Photo by Ben Konfrst on Unsplash

Photo by Ben Konfrst on Unsplash

Why is it important?

Familial exposure is a very strong risk factor for developing sarcoidosis – among the strongest identified to date. Its potential role in disease diagnosis should be further examined. The contribution of genetics in the development of sarcoidosis is found to be much lower than it was previously perceived (39% versus 60–70%). This highlights the importance of environmental factors in disease development, which should be the focus of future research.

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