Response to intravenous iron in patients with iron deficiency anemia (IDA) and restless leg syndrome (Willis–Ekbom disease)

• Seventy-six percent of patients suffering from RLS with iron deficiency anemia (RLS–IDA) improved with administration of 1000 mg intravenous (IV) iron.
• The RLS–IDA response to 1000 mg IV iron was less for African-Americans than Whites.
• Twenty-four percent IV iron RLS–IDA treatment failure was greater than expected.
• RLS–IDA IV iron treatment failures showed low hemoglobin levels after administration of IV iron.
• The IV iron treatment of RLS–IDA may require doses >1000 mg for some patients.

ObjectivesIron deficiency anemia (IDA) engenders restless legs syndrome (RLS, aka Willis–Ekbom disease). Intravenous (IV) iron can rapidly reverse IDA and would be expected to similarly reverse RLS caused by IDA. This is the first consecutive case series evaluating the effects of IV iron therapy on RLS occurring with IDA (RLS–IDA).MethodsRLS–IDA patients were evaluated before and 7–12 months after a 1000-mg IV infusion of low-molecular-weight iron dextran (INFeD@) using validated questionnaires and standardized telephone interview. Patients were classified as respondent versus nonrespondent for RLS improvement.ResultsFollow-up data were obtained on 42 (70%) of 60 consecutive RLS–IDA patients. The symptoms of RLS were reduced in 76% (32/42) with 47% (20/42) showing an extended response lasting >6 months. The response did not relate to age or gender, but tended to be less among African–Americans than Whites (40% (2/5) vs. 81% (30/37), p = 0.078). White respondents versus nonrespondents had higher hemoglobin levels after treatment (12.1 vs. 11.3 g/dl, p = 0.03).ConclusionsRLS–IDA is reduced after administration of IV iron in most cases, but the 24% failing to respond was higher than expected. The nonrespondents all showed below-normal hemoglobin levels (<12.5 g/dl) suggesting a failure of adequate treatment of the iron deficiency. IV iron treatment of the RLS with IDA likely requires ensuring more than minimally adequate body iron stores to support iron delivery to the brain. For some, this may require a dose higher than the customary 1000-mg IV iron used for the treatment of either IDA or RLS alone.