Conference Coverage

Scandinavian studies shed light on OA inheritance



– Patients with osteoarthritis often want to know if their debilitating disease is likely to be passed on to their children. Karin Magnusson, PhD, believes she can answer that question based upon an analysis of two large Nordic studies.

Dr. Karin Magnusson of Lund University, Sweden Bruce Jancin/MDedge News

Dr. Karin Magnusson

“OA in the mother, but not in the father, increases the risk of surgical and clinically defined hip, knee, and hand OA in the offspring, and particularly in daughters,” she reported at the OARSI 2019 World Congress.

Dr. Magnusson, an epidemiologist at Lund (Sweden) University, and her coinvestigators, turned to the Musculoskeletal Pain in Ullensaker Study (MUST) of 630 individuals aged 40-79 with rheumatologist-diagnosed hand, hip, or knee OA by American College of Rheumatology clinical criteria and their offspring, as well as the Nor-Twin OA Study of 7,184 twins, aged 30-75, and their children. Linkage with a national registry that records virtually all joint arthroplasties performed in Norway enabled the investigators to identify which subjects in the two studies had joint surgery for OA, she explained at the meeting, sponsored by the Osteoarthritis Research Society International.

The main outcome in this analysis was the relative risk of hip, knee, or hand OA in the sons and daughters of families in which a parent had OA at those sites, compared with the rate when neither parent had OA. The key finding: If the mother had OA, her daughters had a 13% increased risk of OA in MUST and a 44% increased risk in the Nor-Twin OA Study when compared with daughters of women without OA. In contrast, the sons of a mother with OA had no significant increase in risk of OA. And when OA was present in the father, there was no increased risk of OA at any site in his daughters or sons.

“The implication is the heredity of OA is linked to maternal genes and/or maternal-specific factors, such as the fetal environment,” according to Dr. Magnusson.

And for clinical practice, the implication is that it’s important to ask about family history of OA, and in which parent, to better predict future risk of disease transmission to the children, she added.

These Norwegian study results open the door to exploration of the possible role of mitochondrial DNA in familial clustering of OA, since mitochondrial DNA is inherited only from the mother, Dr. Magnusson noted.

David T. Felson, MD, rose from the audience to say, “I’m a little bit worried” about the fact that when he and other Framingham Heart Study investigators looked specifically for possible mother/daughter, mother/son, father/daughter, and father/son associations for knee and hip OA, “we really didn’t find any.

“You can go through all of the explanations that you want about maternal inheritance, but I’m not sure that’s the best explanation. It might just be that what’s going on here is you’re seeing guys who are relatively young and who got their OA through injury or sports, which is fairly common in young men, and not through inheritance,” said Dr. Felson, professor of medicine and epidemiology at Boston University.

So a third observational study in an independent cohort might be needed as a tie breaker regarding the issue of OA inheritance.

Dr. Magnusson reported having no financial conflicts regarding her study, conducted free of commercial support.

SOURCE: Magnusson K et al. Osteoarthritis Cartilage. 2019 Apr;27[suppl 1]:S47, Abstract 33

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