Is there any scientific information available on how likely it is that a child with one parent with rheumatoid arthritis will have the same condition? I know there's probably not going to be any hard numbers available, but are there any studies at all on this?
The most straightforward study I could find was Koumantaki et al. (1997), which found several odds ratios for developing rheumatoid arthritis:
- 4.4 for individuals having a first degree relative with the disease.
- 5.4 for individuals having a female first degree relative with the disease.
- 7.0 for females having a first degree relative with the disease.
- 4.8 for females whose mother has the disease.
- 8.6 for individuals whose mother has the disease.
- 1.1 for females whose father has the disease.
- 1.9 for individuals whose father has the disease.
An odds ratio of X means that a person is with the given characteristic is X time more likely to have the disease than a person without it. The higher the odds ratio, the greater the chance of the individual inheriting the disease. From this, it is easy to see that those with mothers with rheumatoid arthritis were more likely to inherit it, especially if the individuals were female.
A different study, the GoRA study (summary) found that
if one of your parents, or a sibling (one of your brothers or sisters) has RA, your risk of developing RA will be slightly higher (around a 16% chance) than someone that does not have a family member affected with this illness (around a 0.8% chance).
This would seem to give an odds ratio of about 20 - much higher than any of the other results.
In addition, I've found numbers from Arthritis Research UK (no studies cited) which says that the probability of a child getting rheumatoid arthritis from a parent is about 1-3%.
Going even further, a New York Times Health article claims that
Some people may inherit genes that make them more susceptible to developing RA, but a family history of RA does not appear to increase an individual's risk.
It also goes along with Koumantaki et al.'s findings that women are more likely to get the disease than men.
It seems like the jury is still out on this, although most studies of the genetics behind rheumatoid arthritis focus on which genes might be transferred, or related hypotheses. Many authors conclude that more research on the subject is needed, especially as the origins of the disease are not well known.