Currently, it is unknown whether neuropathic pain or the inflammatory component predominantly causes pain in the skin, muscles, or joints in patients with sarcoidosis and SFN. Understanding this distinction is crucial for applying an effective therapy strategy and is essential to improving clinical care for this patient population. With our newly developed SFN phenotyping questionnaire (SFNPQ), we measure patient-reported symptoms at the level of the skin, muscles, and joints to identify the prevalence in patients with sarcoidosis, with and without SFN. Methods Ethics This study received approval from the local Ethics Committee (Medical Research Ethics Committees United, Nieuwegein, the Netherlands R19.080). Both verbal and written consent were obtained prior to the study. Furthermore, the study adhered to the Declaration of Helsinki and Good Clinical Practice (GCP) guidelines. Design This research was a prospective, cross-sectional, and observational study conducted from January 2021 to September 2022 at the outpatient clinic of St. Antonius hospital, a tertiary referral center specializing in sarcoidosis and interstitial lung diseases (ILD) in the Netherlands. The study included patients aged 18 to 75 years with sarcoidosis, with and without symptoms and clinical signs of SFN. The diagnosis of sarcoidosis was made in accordance with the American Thoracic Society guidelines.17 Exclusion criteria were large fiber neuropathy, other diseases with a risk for developing (poly)neuropathy or SFN, diseases affecting sensory nerve function, pregnancy, psychological problems, language barriers, glucose intolerance, rheumatoid arthritis, vitamin B12 deficiency, and excessive alcohol consumption, as assessed by the treating physician. Neuropathy Assessment Neuropathy assessment was conducted as previously described.18 Briefly this included a diagnosis of “probable SFN” based on symptoms, clinical signs during neurological evaluation (presence of two or more clinical signs such as hypoalgesia, allodynia, hyperalgesia, and thermal hypoesthesia; see Table 1 for a summary of symptoms), and normal nerve conduction studies, as defined by the Besta criteria.19 Table 1 Summary of symptoms related to small fiber neuropathy General Symptoms Sensory disturbances Autonomic dysfunction Fatigue Neuropathic pain Skin changes Cognitive disturbances Burning sensations Sweating abnormalities Headache Paresthesia Vision Widespread musculoskeletal pain Hypoesthesia/numbness Urinary tract Tingling Dry mouth Itching Gastrointestinal dysmobility Frostbite-like sensations Orthostasis Bedsheet/clothing intolerance Palpitations Stocking-glove / random / migratory and/or intermittent Bowel or bladder changes Hot flushes Sexual dysfunction 4 71 4
RkJQdWJsaXNoZXIy MjY0ODMw