Co-localization of pain and reduced intra-epidermal nerve fiber density in individuals with HIV-associated sensory neuropathy

IntroductionThere is poor correlation between decreases in intra-epidermal nerve fiber density (IENFD) and the presence of pain in HIV-associated sensory neuropathy (HIV-SN) and other painful distal symmetrical polyneuropathies.ObjectiveWe investigated whether in individuals with HIV-SN, having pain at the ankle skin biopsy site was associated with lower IENFD compared to when there was no pain at the ankle biopsy site.MethodsWe recruited 15 individuals with symptomatic HIV-SN. Nine had pain at the site where the ankle biopsy was taken, while six did not. Skin punch biopsies for IENFD quantification were taken from the ankle and the thigh. Contrasts between the two groups were made using the overlap of confidence interval (CI) method.ResultsIENFD was substantially lower in the group that had pain at the site of the ankle biopsy compared to the other group [6.6 (CI: 5.3 to 7.2) vs. 3.3 (CI: 10.0 to 15.0) fibers/mm]. However, there was no group differences at the thigh biopsy site [15.6 (CI: 15.0 to 15.9) vs 16.2 (CI: 14.5 to 17.8) fibers/mm]. When taking the ratio of ankle IENFD:thigh IENFD, the point estimate for the pain at the ankle group [0.43 (CI: 0.36 to 0.48)] was about half that of the other group [0.81 (CI: 0.68 to 0.87)].ConclusionThus, co-localization of pain to the ankle is associated with meaningful decreases in ankle IENFD.SummaryHaving pain at the ankle biopsy site is associated with lower intra-epidermal nerve fiber density compared to not having pain at the ankle biopsy site.