12 Measurement of patient-reported outcomes Patient-reported SFN can be evaluated with the SFN-screening list (SFNSL).50 The SFNSL is a generic questionnaire that can also be used in sarcoidosis-associated SFN. The SFNSL evaluates specific symptoms of SFN, however, it does not distinguish between different phenotypes of SFN. Both for clinical management as well as for research on improvement of treatment options there is need for fine-tuning in assessment of SFN symptoms in sarcoidosis patients. First, distinguishing between length-dependent, non-length-dependent, intermittent and continuous pain is important. Moreover, patients should be able to indicate the location of pain specific to pain on the skin, muscles, joints or other levels. Finally, assessment of either intermittent or continuous pain, is mandatory. This thesis investigates whether a new questionnaire is meeting these requirements. General treatment of SFN Treatment of SFN generally focusses on treating the underlying condition and providing symptom relief. In cases of persistent painful SFN symptoms, anti-depressants, serotonin-norepinephrine reuptake inhibitors (SNRI), anticonvulsants, or pain-relieving drugs can be considered as first-line treatment (Figure 4).46 Second-line treatment options include anticonvulsants and opioids. Finally, third line treatment is limited to anticonvulsants. Therapeutic strategies are primarily symptomatic, achieving about 50% pain relief in only half of patients.51 Figure 4 General symptomatic treatment of small fiber neuropathy (SFN) treatment via a step-up approach. When persistent painful SFN symptoms are present, first line, second line, or third line treatment may be considered including tricyclic anti-depressants (TCA), serotonin norepinephrine reuptake inhibitors (SNRI), anticonvulsants, paracetamol (PCM), non-steroid anti-inflammatory drugs (NSAIDs), or opioids. Specific disease management strategies are not shown in the figure. Sarcoidosis This thesis focuses on SFN associated with sarcoidosis. Therefore, this section describes the background of this disease. Sarcoidosis is a granulomatous, multisystem disorder of unknown cause, mainly affecting lungs and lymph nodes. However, virtually any organ can be affected leading to a heterogeneous clinical presentation. The disease resolves spontaneously within 2-5 years in most patients (60%), but in approximately 40% of cases, it persists, often requiring years of treatment and monitoring.52,53 Pharmacological treatment of sarcoidosis is primarily aimed at preventing specific organ damage or alleviating symptoms and includes corticosteroids, methotrexate, disease-modifying anti-rheumatic drugs (DMARDs), or anti-tumor necrosis factor alpha (anti-TNF-α) treatments like infliximab.3,4 Many symptoms in patients with sarcoidosis are not organ-specific and include fatigue, cognitive failure, or symptoms related to sarcoidosis-associated SFN.54 Of these symptoms, fatigue is the most frequently reported in patients with sarcoidosis, with an estimated prevalence between 6090%, and it has the greatest impact on daily life.54 1 13 1
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