Figure 4 Percentage of participants reporting symptoms in the head, thorax, arms, hands, back/abdomen, legs, and feet. Sarcoidosis patients were divided into those with probable small fiber neuropathy (Prob. SFN), no SFN and healthy controls (HC). P-values were presented as stars: *<0.05; **<0.01; ***<0.001;****<0.0001. Discussion This study investigated the prevalence of skin, muscle and joint complaints in healthy controls and patients with sarcoidosis, both with and without SFN. The prevalence of granulomas in these organs was established, along with the prevalence of organ-related symptoms reported during consultations. The newly developed SFNPQ was introduced to identify organ symptoms in specific body areas. Exteroceptor small nerve fibers are responsible for the sensation of pain, temperature, touch, and pressure.22 These fibers are primarily affected in SFN, and manifesting symptoms at a cutaneous level.23 Assessment of cutaneous symptoms revealed more frequent symptoms in patients with sarcoidosis and probable SFN, particularly in the hands, back/abdomen, and feet. Proprioceptor small nerve fibers are responsible for the sense of movement and position.22 Dysfunction in these fibers may result in muscular symptoms, which are not well-established in SFN literature. A small group of patients with isolated muscle cramps (n=12) was investigated, and SFN was found in 60% of patients with decreased IENFD.24 Muscle cramps, acknowledged as symptoms of SFN, often overlap with fibromyalgia symptoms.23 Muscular symptoms were more frequently observed in patients with sarcoidosis and probable SFN in the thorax, arms, back/abdomen, and legs. Painful joints are relatively unknown in patients with SFN.25 Although free nerve endings of small nerve fibers are present in joints,22 joints pain is often interpreted as arthritis, rheumatism or fibromyalgia. Our cohort showed a high prevalence of joint symptoms in patients with sarcoidosis. Moreover, patients with sarcoidosis and probable SFN reported more painful joints in the feet. Only 33% of patients with sarcoidosis and SFN mentioned joint pain during consultations with pulmonologists or neurologists, while 92% indicated joint pain according in our phenotyping questionnaire. This highlights a lack of awareness for joint pain in patients with sarcoidosis and SFN. Since, no diagnostic methods exist to test free nerve endings in joints, it remains unknown whether these symptoms were truly caused by SFN or had another (immunologic) origin. A significantly higher prevalence of joint symptoms in patients with sarcoidosis without SFN might be due to bias caused in our patient population. About half of the group of patients with sarcoidosis without SFN presented with symptoms associated with SFN but without clinical signs of SFN. The other 4 75 4
RkJQdWJsaXNoZXIy MjY0ODMw