Effect of PUVA therapy on melanocytes and keratinocytes in non-segmental vitiligo: histopathological, immuno-histochemical and ultrastructural study

Background and Aims: Psoralen ultraviolet A (PUVA) is an important modality in treating vitiligo. Its effect on melanocytes and keratinocytes is not sufficiently studied. In this work, we investigated 30 cases of non-segmental vitiligo regarding the changes of melanocytes and keratinocytes in both vitiliginous and nearby areas before and after PUVA therapy. Methods: Three skin biopsies were obtained from each patient from the vitiliginous, marginal and perilesional areas before and after 12 months of PUVA. Biopsies were examined histologically using haematoxylin and eosin, Masson-Fontana stains and 3,4-dihydroxyphenylalanine (DOPA) reaction and histochemically using human melanoma black-45 (HMB-45) antibody while ultrastructural examination was performed on six patients. Control biopsies were taken from five healthy volunteers. Results: In 10% of pretreated biopsies from the centre of vitiligo lesions, scanty melanocytes were detected histologically and ultrastructurally, while they did not stain with DOPA or HMB-45 antibody suggesting that these melanocytes were inactive. Moreover, degenerative changes were detected by electron microscopy in both melanocytes and keratinocytes in all areas. After PUVA therapy, obvious improvement of the histopathological changes occurred with significant increase in active melanocytes. The degeneration of melanocytes and keratinocytes was also reduced at the ultrastructural level. Conclusion: Vitiligo affects both melanocytes and keratinocytes causing degenerative changes. These changes were present in both the leucodermic and the apparently normal perilesional skin. PUVA increases the number of active epidermal melanocytes in the three tested areas and recovers the melanocyte and keratinocyte degeneration.