Small fiber neuropathy (SFN) is characterized by neuropathic pain and autonomic dysfunction. The affected functions cannot be actively and/or consciously influenced, such as heart rhythm, sweating pattern and problems with micturition (urination) and defecation. Currently, the diagnosis is made based on the clinical picture combined with an abnormal temperature threshold testing and/or abnormal skin biopsy, without abnormalities on nerve conduction studies (NCS). Sometimes, we see patients who do have neuropathic pain and autonomic dysfunction, suspected for SFN but cannot be diagnosed with the mentioned examinations. Thus, at this time there is no gold standard. For this reason, research was conducted into techniques that can make an (additional) contribution to set the diagnosis. In addition, in this dissertation attention was paid to the genetic contribution to SFN.