Hydroxyproline excretion in psoriasis and psoriatic arthritis

: In the morning urine of 24 patients with psoriasis and that of 24 patients with psoriatic arthritis, we determined the excretion of hydroxyproline (mg HP/mumol crea), after preceding diet low in collagen. Surprisingly, psoriatic patients without articular involvement showed a significantly higher excretion of HP than those with psoriatic arthritis. Further differentiation revealed that there were no clear-cut correlations between the amount of HP excretion and the activity of the articular process; we proved, however, that the amount of HP excretion was definitely related to the activity of the skin eruptions in both groups of patients. We discuss whether an osteopathy pathogenetically associated with the skin disease (irrespective of synovitis in psoriatic arthritis) may possibly be responsible for these results.