Alpha 1-proteinase inhibitor in psoriasis: reduced activity in symptom-free patients and during flare.

The aim of this study was to quantitate the active fraction of the alpha 1-proteinase inhibitor (alpha 1-PI) in psoriasis. Serum proteinase inhibitory capacity was measured vs porcine pancreatic elastase of a known active fraction against its specific substrate (Suc-Ala3-pNA). The inhibitory capacity was determined in 21 symptom-free patients, 134 patients with skin lesions, and 23 healthy volunteers. Alpha 1-PI was found to be significantly decreased in symptom-free patients and in those with stationary lesions, in a manner similar to the reduced activity of neutrophil proteinases, elastase, and cathepsin G. The synthesis of alpha 1-PI was stimulated during the appearance of active psoriatic lesions, but to a much lesser degree in patients with early onset (less than or equal to 21 years) than in patients with late onset of psoriasis (greater than 21 years). The early onset subgroup differed by a more frequent familial occurrence of psoriasis and a more severe course of the disease. The data indicate that the regulation of the proteinase-alpha 1-PI system in psoriasis is abnormal and this may contribute to the pathogenesis of the disease. The decreased alpha 1-PI during flare may be responsible for the disease activity, at least in patients with early onset of psoriasis.