Two subpopulations of patients with early and late onset of psoriasis differ regarding alpha 1-proteinase inhibitor activity.

Two subpopulations of patients with psoriasis were identified when activity of alpha 1-proteinase inhibitor was analysed according to the patient's age at onset of the disease. Patients with early onset had more active lesions, high incidence of familial psoriasis, and reduced alpha 1-proteinase inhibitor during flare similar to that activity in remission. In contrast, alpha 1-proteinase activity increased significantly during flare in patients with late onset (above 21 yrs of age) in response to the inflammatory process in the psoriatic skin.