Rheumatoid arthritis A. clinical and laboratory manifestations

Rheumatoid arthritis (RA) is a chronic systemic autoimmune inflammatory disease that affects all ethnic groups throughout the world. Females are 2.5 times more likely to be affected than males. The onset of disease can occur at any age but peak incidence occurs within the fourth and fifth decades of life. The average annual incidence of RA in the United States is 0.5 per 1000 persons per year (1). The overall prevalence of RA is 1% to 2%, and it steadily increases to 5% in women by the age of 70 (2). However, there are differences in prevalence rates of RA in various ethnic groups, ranging from 0.1% in rural Africans to 5% in Pima or Chippewa Indians (3). Many factors contribute to the risk of developing RA and are reviewed in the following chapter (see Chapter 6B).