Fatigue, restless legs syndrome, pain and cognitive impairment in patients with sarcoidosis associated small fiber neuropathy

60-90% of sarcoidosis patients suffer from fatigue and 16-52% of sarcoidosis patients experience restless legs syndrome (RLS) symptoms. It is known that RLS disturbs sleep quality and therefore might be related with increased fatigue. Fatigue has a negative impact on cognition and pain sensation, which impairs quality of life. It is unknown whether the burden of these symptoms increases when sarcoidosis patients also suffer from small fiber neuropathy (SFN). Healthy controls and sarcoidosis patients were included to answer the fatigue assessment scale (FAS), RLS rating scale, visual analogue scale score for pain and the cognitive failure questionnaire. The prevalence and burden of fatigue, RLS, pain, SFN and cognitive failure were investigated. Additionally, a correlation between these symptoms was investigated. 20 healthy volunteers, 49 patients with sarcoidosis without SFN (no SFN) and 48 patients with sarcoidosis and probable SFN (prob. SFN) were included. The FAS showed the highest prevalence of fatigue (84% in no SFN, 97% in prob. SFN), followed by pain (33% in no SFN, 85% in prob. SFN), RLS (40% in no SFN, 67% in prob. SFN) and cognitive failure (35% in no SFN, 46% in prob. SFN). Sarcoidosis patients with established SFN showed an increased prevalence and higher burden of fatigue, RLS, pain and cognitive failure. Moreover, moderate to strong correlations were found between the symptoms.