Genome-wide etiology analysis of autoimmune hypothyroidism supports somatic mutations of at-risk DNA as the underlying cause.

Autoimmune hypothyroidism (AIHT) is the most common autoimmune disease. Through an unidentified mechanism, the immune system attacks the thyroid gland, destroys thyroid follicular cells, and causes hypothyroidism. A new theory poses that all DNA is continuously damaged and, as a result, is exposed to somatic mutations at a constant rate. Based on this theory, several assumptions related to epidemiology and DNA sequence can be made. These have been summarized as a method called genome-wide etiology analysis (GWEA) to facilitate the interpretation of GWAS results of autoimmune diseases. Here, GWEA is applied to AIHT. The results show that existing epidemiological and genomic data of AIHT adhere to the principles of GWEA. Therefore, AIHT appears to be the result of somatic mutations in people at risk for the disease. AIHT develops once sufficient mutations create a new "autoimmune pathway" driven by non-self-signal and supported by neopeptide formation and signal amplification. Given the random nature of somatic mutations throughout life, the new theory explains why some people with AIHT develop additional autoimmune diseases, why family members may develop a range of non-AIHT autoimmune diseases, why the age of onset cannot be predicted, and why AIHT is transferred to the following generations through dominant inheritance with delayed, incomplete penetrance.