Where Does It All Itch? Exploring the Characteristics of Pruritus in Small Fiber Neuropathy.

Background: Chronic itch, or pruritus, is a common discomfort of the skin. Chronic itch has been described as a symptom of small fiber neuropathy (SFN), a disorder affecting the small myelinated Aδ- and unmyelinated C-fibers. While prior studies report itch rates in SFN ranging from 63%-68%, a distinct pattern has not been identified.

Aim: This study aimed to describe the clinical characteristics of itch in a large cohort of SFN patients.

Methods: Between May 2016 and August 2022, 1415 patients filled out an exploratory questionnaire about characteristics of their itch symptoms. 83% were diagnosed with SFN based on the Besta criteria.

Results: Itch was reported in 66% of SFN patients, mainly experienced as tickling, prickling, and tingling sensations. Itch was most common in the evening, with 98% reporting continuous or episodic symptoms during this time. The itch was predominantly localized to the distal extremities, especially the lower legs and feet (over 50% of patients), with additional reports on the back (25%) and face (27%). Unlike the typical stocking-glove distribution seen with neuropathic pain, itch showed a slightly more proximal locus. SFN patients were more likely to report itching in the hands and feet than non-SFN patients.

Interpretation: This study reveals that itch in SFN is a frequent, heterogeneous symptom that may differ from neuropathic pain in its distribution. Itch, particularly in the hands and feet, may provide diagnostic guidance and suggest SFN as a potential diagnosis. This finding warrants further research on itch mechanisms and its diagnostic value in SFN.