Psoriasis and skin pain: instrumental and biological evaluations

The prevalence of skin pain and the molecular mechanisms responsible for pain in psoriasis remain unclear. This study assessed skin pain in 163 patients (98 males, 65 females, range 18-81 years) with plaque psoriasis, evaluating: the subjective/objective features of this symptom compared with clinical severity of the disease; and the role of interleukin (IL)-33, (involved in both psoriasis and pain pathogenesis), in psoriasis-related pain. Clinical measures used were a questionnaire, plaque Physician Global Assessment (PGA) index, pressure algometry to measure pain threshold and tactile/thermal sensitivity test. IL-33 gene expression was examined in vivo (n = 12) in patients skin and through an ex vivo model of nociception using sodium dodecyl sulphate. Of the psoriatic patients 43.6% reported skin pain during the previous week; itchy, unpleasant, aching, sensitive, hot/burning, tender and cramping were the most reported qualities. Patients' pain threshold decreased with increasing PGA index and pain intensity. Sensitivity to touch/heat was reduced in lesional skin, compared with unaffected psoriatic skin. IL-33 expression was increased in lesional skin of patients reporting pain and in the ex vivo system. In conclusion, symptoms of skin pain should be taken into account in the management of psoriasis.