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Fetal DNA may spark Sjögren’s syndrome

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Sjögren’s syndrome (SS) may have its origins in fetal DNA from an earlier pregnancy. A molecular study has shown for the first time male fetal DNA in the inflammatory lesions. Male specific DNA occurred in biopsy specimens from affected salivary glands in a significant proportion of mothers with SS who had one or more sons. It also showed up in cells from lung aspirates from a significant proportion of those mothers with interstitial lung lesions. The sequence was absent from mononuclear cells from the blood and all samples from the controls. Women with SS and no sons did not have the sequence, apart from two—explained by a previous abortion and a blood transfusion. All three biopsy specimens tested by fluorescence in situ hybridisation (FISH) were positive.

Fifty six women with SS were tested. Blood was obtained from 27, biopsy specimens from 42, and cells from bronchiolar lavage fluid from nine. The controls were eight healthy women volunteers with no previous pregnancy, 10 women with mucocoele but no SS, and 15 women with other lung diseases, respectively. Male specific DNA was detected by nested PCR and FISH.

Male DNA, probably from fetal cells in the mother’s circulation, occurs in skin lesions due to other autoimmune diseases, though a universal link is disputed. Lesions of SS and graft versus host disease are similar, suggesting a similar disease mechanism.

Larger scale testing is needed; also microchimerism as described here, but with female fetal cells, might feature in pathogenesis.