Genetic susceptibility and the link between cat exposure and rheumatoid arthritis

Latitude gradient influences the age of onset in rheumatoid arthritis patients

The mean age of rheumatoid arthritis (RA) onset is around 50 years as reported in several clinical trials involving Caucasian patients. However, clinical observations suggest that Mexican RA patients' disease is initiated at a younger age. The objective of the study was to assess whether the age of onset of RA is different in Mexican and in Canadian RA patients. Certified rheumatologists from Canada and Mexico directly interviewed consecutive RA patients attending their clinics regarding the date patients first noticed a swollen joint. None of the participant rheumatologists were aware of the primary aim of this exploratory study at the time of the interviews. Data was gathered from 161 Mexican (91% women) and 130 Canadian (77% women) RA patients collected by three rheumatologists in each country. Duration since disease onset was not different within countries (mean 95% confidence interval [CI] for differences -10 to 16 years, p = 0.12 for Canadians, and -6 to 10 years, p = 0.26, for Mexicans). However, there was a significant difference between the two countries. Mexicans patients on average developed RA almost 12 years younger than Canadians (95% CI for difference 9 to 15 years, p < 0.001). Frequency distribution showed that 35.5% of Canadians but only 4% of Mexicans had the onset of the disease after the age of 55 (all p < 0.001). It appears that RA begins at a much younger age in Mexican than Canadian patients. If this were confirmed after controlling for different confounders and biases, it would have important societal, economic, and therapeutic implications.

The schizophrenia-rheumatoid arthritis connection: infectious, immune, or both?

Schizophrenia and rheumatoid arthritis share an impressive number of similarities. Both are chronic, relapsing diseases of unknown etiology. Both became prominent in the early 19th century and have prevalences of approximately 1% in North America and Europe. Both run in families, have pairwise concordance rates of approximately 30% among monozygotic twins, and are more common among individuals born in urban areas. For both diseases, studies have reported greater exposure to cats in childhood than in controls. Both diseases have been associated with similar class II HLA antigens. Both have also been suspected of having infectious etiology, with similar agents--retroviruses, herpesviruses including EBV, and Toxoplasma gondii--having been associated in some cases. Since there is also a well-documented inverse correlation between these two diseases, it is possible that they share a common infectious and/or immune etiology and that once a person gets one of the diseases then they are relatively immune to the other.

Approaches to rheumatoid arthritis in 2000

The year 2000 was characterized by euphoria among clinicians based on the continued and consolidated success of tumor necrosis factor (TNF) inhibition but also by problems caused by the high cost of this therapy. Looking at the risks and adverse effects has only begun, and there is so far a remarkable lack of publications dealing with this topic. Leflunomide also emerges as an established disease-modifying antirheumatic drug (DMARD). Other therapies include the cyclooxygenase-2 (Cox-2) inhibitors, which are tolerated better by the gastrointestinal system but raise concerns regarding thromboembolism in patients at risk. The enthusiasm regarding Cox-2 inhibitors is somewhat tempered by recent reports of thromboembolic complications, although those have been rare. The advances in research regarding mechanisms of inflammation and pathogenesis continue to generate new therapeutic approaches, which, however, remain mostly experimental. The complexity of genetics has been emphasized by reports on susceptibility and severity relation to TNF, mannose-binding lectin, and gamma-interferon polymorphism. Epidemiologic studies focusing on prevalence, incidence and outcome continue to deliver conflicting messages. One major worry relates to chronic inflammation in RA and other rheumatic diseases as putative cause of accelerated atherosclerosis.