Fast Five Quiz: Joint Pain

Herbert S. Diamond, MD


February 12, 2019

First-degree relatives of individuals with RA are at two- to threefold higher risk for the disease. Disease concordance in monozygotic twins is approximately 15% to 20%, suggesting that nongenetic factors play an important role. Because the worldwide frequency of RA is relatively constant, a ubiquitous infectious agent has been postulated to play an etiologic role. Women are affected by RA approximately three times more often than men, but sex differences diminish in older age groups.

Sex hormones may play a role in RA, as evidenced by the disproportionate number of women with this disease, its amelioration during pregnancy, its recurrence in the early postpartum period, and its reduced incidence in women using oral contraceptives. Hyperprolactinemia may be a risk factor for RA.

For many decades, numerous infectious agents have been suggested as potential causes of RA, including Mycoplasma organisms, Epstein-Barr virus, and rubella virus. This suggestion is indirectly supported by the following evidence:

  • Occasional reports of flulike disorders preceding the start of arthritis

  • The inducibility of arthritis in experimental animals with different bacteria or bacterial products (eg, streptococcal cell walls)

  • The presence of bacterial products, including bacterial RNA, in patients' joints

  • The disease-modifying activity of several agents that have antimicrobial effects (eg, gold salts, antimalarial agents, minocycline)

Read more information on rheumatoid arthritis.


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