[Sequence variants of unknown significance in small fiber neuropathy : Characterization of a heterogeneous patient population].

Background: In almost half of patients suffering from small fiber neuropathies (SFN), the etiology remains elusive. For these patients with "idiopathic SFN", symptomatic analgesic therapy is the only option. Reports on a potential genetic background of neuropathic pain syndromes are increasing and particularly in SFN patients, several genetic variants were found mainly located in genes encoding voltage-gated sodium channels. Although up to 30% of SFN patients show genetic alterations, most of these remain of "unknown pathogenic significance" and little is known about "genetic SFN".

Objectives: The study aimed to determine clinical characteristics of SFN patients carrying a rare genetic variant of unknown significance in pain-associated genes.

Materials and methods: From 2015 to 2020, 66 patients with primarily idiopathic SFN were examined and rare gene variants of unknown significance detected in 13/66 (20%) of these. A detailed medical history with focus on pain was recorded and patients filled in standardized questionnaires to assess physical and emotional burden due to pain.

Results: The authors found 13/66 (20%) patients with rare variants of unknown significance located in pain-associated genes who reported pain refractory to analgesic treatment, a higher number of external factors influencing clinical symptoms, and a higher level of physical impairment and emotional stress due to pain compared with patients without such genetic variants.

Conclusions: Early genetic assessment is recommended to optimize the management of patients with potentially hereditary SFN. Early access to rehabilitation and mental support as well as a consequent elimination of external triggering factors should be granted.