Xerosis and hypohidrosis, the presence of pruritogenic cytokines (histamine, kallikrein, interleukin- (IL-) 2, acetylcholine, and other substances released by histamine-mediated mast cell stimulation), as well as secondary hyperparathyroidism, and immune-inflammatory reactions, have been proposed as reasons for the occurrence of UP [20, 21]. This evidence concerns the gene KLK4 and secondary hyperparathyroidism.