Rheumatologic serologies in secondary restless legs syndrome

Diagnostic criteria for restless legs syndrome (RLS) have been established; however, the pathophysiology of this common condition remains elusive. Several secondary forms of RLS potentially include renal failure, iron deficiency, pregnancy, and neuropathy. RLS has also been reported in approximately 25% of patients diagnosed with rheumatoid arthritis and Sjögren's syndrome. We performed clinical and serologic evaluations on 68 patients diagnosed with RLS to determine how many may have concurrent rheumatologic disease that could be causing their RLS symptoms. We compared these with other postulated secondary causes of RLS. No patient had clinical evidence of rheumatologic disease, and only four had any positive serologic evaluations (two positive SSA/SSB and two mildly elevated RF titers). Three of these had a positive family history for RLS. Patients without a family history of RLS did have lower ferritin levels, more cases of neuropathy, and an older age at symptom onset. We do not think rheumatologic disease represents a significant secondary cause of RLS and do not recommend serologic investigation unless there are overt clinical signs. In contrast, our study suggests that neuropathy and serum iron deficiency do represent secondary forms of RLS.