Improving acne keloidalis nuchae with targeted ultraviolet B treatment: a prospective, randomized, split-scalp comparison study.

Acne keloidalis nuchae (AKN) is a chronic scarring folliculitis with fibrotic papules on the occipital scalp. Its treatment is limited and unsatisfactory.,To determine whether targeted ultraviolet B (tUVB) phototherapy will (i) improve the clinical appearance of AKN and (ii) induce extracellular matrix remodelling in affected lesions.,Eleven patients with AKN were enrolled in a prospective, randomized, split-scalp comparison study. One randomly selected side of the scalp was treated with tUVB up to three times weekly for 8 weeks. After week 8, both sides were treated for eight additional weeks. Assessment included lesion counts in two 3 × 3-cm regions of interest (ROIs), one on each side of the scalp (ROI-1: tUVB weeks 0-16, ROI-2: tUVB weeks 9-16), patient self-assessment and analysis of MMP1, MMP9, TGFB1 and COL1A1 mRNA expression by quantitative reverse-transcription polymerase chain reaction.,Before treatment, the mean lesion count was similar between tUVB-treated and untreated sides (14·8 vs. 15·0). After 8 weeks of tUVB, the mean lesion count decreased significantly to 9·4 ± 1·2 (P =  0·03), with no change on the untreated side. With continued treatment, the mean lesion count in ROI-1 decreased further to 7 ± 1·5 (P = 0·04) after 16 weeks of tUVB.,tUVB significantly improved the clinical appearance of AKN, led to patient satisfaction and was well tolerated.