Mast cell activation syndrome (MCAS) is an inflammatory and allergic disorder. We determined the prevalence of Restless Legs Syndrome (RLS) in MCAS since each common syndrome may be inflammatory in nature and associated with dysautonomia.
MCAS subjects were evaluated for RLS by two standard questionnaires. Prevalence comparisons included spouse controls and two prevalence publications. MCAS diagnosis required mast cell (MC) symptoms in ≥2 organs plus ≥1 elevated MC mediators, improvement with MC-therapy, and/or increased intestinal MC density. Clinical variables were studied.
There were 174 MCAS subjects (146 F, 28 M, mean 44.8 years) and 85 spouse controls (12 F, 73 M, mean 50.9 years). MCAS subjects as a whole had a higher prevalence of RLS (40.8%) than spouse controls (12.9%) (P <0.0001) Male MCAS subjects had a higher prevalence of RLS (32.1%) than male controls (12.3%, OR 3.4, CI 1.2-9.7, p=0.025) American men (8.4%, OR 5.2, CI 2.2-12.0, p<0.001), and French men (5.8%, OR 7.7, CI 3.4-17.1, p<0.001). Female MCAS subjects also had a higher prevalence of RLS (42.5%) than female controls (16.7%) but this did not reach statistical significance perhaps due to the sample size of the female controls. On the other hand, female MCAS subjects had a statistically higher prevalence of RLS than American women (10.0%, OR 6.7, CI 4.5-9.7, p<0.0001) and French women (10.8%, OR 6.1, CI 4.4-8.6, p<0.0001).
RLS appears to be associated with MCAS. Effects of MC mediators, inflammation, immune mechanisms, dysautonomia, or hypoxia may theoretically activate RLS in MCAS.

© 2020 American Academy of Sleep Medicine.