In vivo imaging of patients with chronic pruritus of unknown origin reveals partial sweat duct obstruction with partial itch resolution upon retinoid treatment

Background Chronic pruritus of unknown origin (CPUO) is poorly understood and lacks effective treatment options. Objectives We aimed to elucidate abnormalities in the sweat apparatus patients with CPUO, assess efficacy safety systemic retinoids. Methods An initial case–control study included 20 affected five healthy controls, for whom heat sweating were induced, either through a standardized exercise protocol or ingestion hot water. In vivo high-definition optical coherence tomography, whole-body starch-iodine testing, skin biopsy immunofluorescence staining done evaluate duct obstruction. A subsequent retrospective cohort analysis 56 seen at an Itch subspecialty clinic single tertiary referral centre, who failed conventional treatments treated isotretinoin and/or acitretin from May 2014 November 2020. Treatment response retinoids was defined as sustained reduction itch score ≥2/10. Safety assessed by proportion stopping due side effects. Results imaging 19 (95%) revealed features partial keratinaceous obstruction statistically significant luminal dilatation compared controls. Immunofluorescence studies three patients’ paired lesional/non-lesional biopsies dermcidin accumulation within glands coupled leakage itchy skin. Fifty-six (mean [SD] age 55.2 [17.5] years, 69.6% male) Mean (SD) duration 116.3 (140.4) months mean 8.2 (1.8). Forty-one (73.2%) initially received isotretinoin, 15 (26.8%) acitretin. At months, reduced 2.38 (95% CI -3.2 −1.6, p < 0.0001). Thirty-eight (67.9%) had response. Eight (14.81%) achieved 0 1, four 318.5 (291.2) days without relapse. (14.3%) stopped switched retinoid adverse effects, similar incidences between both retinoids, commonest being dryness. Conclusion Based on novel findings physiological identifying we instituted address underlying pathology. therapies, appears safe.