Severely photosensitive psoriasis: a phenotypically defined patient subset.

A subset of patients with chronic plaque psoriasis exhibits severely photosensitive psoriasis (PP) with a pronounced seasonal pattern, but the pathomechanism is not understood. We performed two related studies; first, a detailed clinical characterization of PP, and second, a controlled investigation exploring the underlying pathomechanisms through the assessment of disease onset after photoprovocation. Patients with PP (n=20) showed striking female predominance (19F:1M), very low mean age of psoriasis onset (11 years, range 2-24), family history of psoriasis (13/20), a strong HLA-Cw*0602 association (16/17), and a rapid abnormal clinical response to broadband UVA, comprising erythema+/-scaling plaques (17/20).