Synovial fluid effusions and/or arthritis may be found in patients with chronic lymphocytic thyroiditis (CLT), even in the absence of hypothyroidism. Sometimes these arthropathies can be attributed to the rheumatic diseases frequently associated with CLT, but in some instances the arthritis seems to be independent of any of the diseases known to cause arthritis, and therefore remains unclassified. This study was carried out in an attempt to characterize the type and outcome of arthritis associated with CLT.
We performed a prospective study with a follow-up of 6.42 years (range 4-13) on 33 patients affected with CLT and presenting with arthritis. All conditions known to cause arthritis were previously excluded. Investigations included HLA typing, x-ray of the affected joints and, when possible, synovial fluid (SF) analysis with an interleukin (IL)-1 beta determination. Patients were divided based on their clinical presentation into two groups: those with polyarthritis and those with oligoarthritis.
During the follow-up, 8 out of 16 patients with polyarthritis developed severe rheumatoid arthritis, characterized by bone erosions, high levels of SF IL-1 beta and an increased frequency of HLA DR4. The other 8 patients had polyarthritis in a mild, non-erosive form, which responded well to symptomatic drugs. Oligoarthritis, found in 17 patients, also showed a mild evolution, with frequent spontaneous remissions. The non-rheumatoid polyarthritis and oligoarthritis patients were characterised by the absence of bone erosions, low levels of SF IL-1 beta and an increased frequency of HLA DR3.
We conclude that it is possible to find in association with CLT a type of inflammatory arthritis characterized by a mild, non-erosive evolution, low SF levels of IL-1 beta and an increased frequency of HLA-DR3. This arthritis seems to be independent of thyroid dysfunction and shows a clinical pattern similar to the arthritis usually found in connective tissue diseases.