Evidence of fetal microchimerism in Hashimoto's thyroiditis.

Fetal microchimerism, the engraftment of fetal progenitor cells into maternal tissues, has been implicated in the etiology of autoimmune diseases. We used PCR analysis to determine whether microchimerism occurred in the thyroid glands of female patients suffering from Hashimoto's disease and thus may be involved in its etiology. PCR amplification was performed from thyroid gland specimens using primers unique to a Y-chromosomal sequence (SRY gene) and primers for a sequence that is Y/X-chromosomal homologous except for a 6-bp deletion in the X-chromosomal sequence (amelogenin). Microchimerism was detected in 8 of 17 Hashimoto patients, but in only 1 of 25 controls (nodular goiters). Both groups were of similar age and had comparable numbers of pregnancies and numbers of sons. All individuals with microchimerism had given birth to at least 1 son. Our results show that microchimerism is significantly more common in Hashimoto patients than in patients suffering from nodular goiter. We therefore suggest that microchimerism might play a role in the development of Hashimoto's disease, although we cannot completely eliminate the hypothesis that microchimerism is just an "innocent bystander" in a process triggered by other mechanisms.