The use of serologic markers for collagen synthesis and degradation in systemic sclerosis.

Systemic sclerosis is characterized by excessive accumulation of collagen in all involved organs. Serum markers of collagen synthesis and degradation, the aminoterminal propeptide of type III procollagen (PIIINP), the carboxyterminal propeptide of type I procollagen (PICP), and the crosslinked telopeptide of type I collagen (ICTP), can be measured. Our purpose was to investigate these markers in different subgroups of untreated patients with systemic sclerosis and in patients before and after various types of therapy. PIIINP and PICP were also investigated in blister fluid from involved and uninvolved skin. Sera from 97 patients and suction blister fluid from 13 patients were radioimmunoassayed. The highest levels of PIIINP and PICP were found in blister fluid from involved skin. Patients with systemic sclerosis had higher serum levels of PIIINP than control subjects. The highest levels were found in patients with diffuse cutaneous systemic (type III) sclerosis; increased serum PIIINP was also characteristic of type II limited cutaneous systemic sclerosis. Most patients with limited cutaneous type I systemic sclerosis had normal levels. Serum PICP was within normal limits in all three types of systemic sclerosis. Variations in ICTP type I collagen degradation in general followed PICP. Immunosuppressive drugs significantly reduced PIIINP, whereas no significant decrease was found after photopheresis. PICP and ICTP also diminished after treatment with D-penicillamine and cyclophosphamide given together with prednisone. PIIINP can be recommended for monitoring collagen synthesis in systemic sclerosis. Our data support the use of immunosuppressive therapy for this disease.