Type III collagen aminopropeptide levels in serum of patients with progressive systemic scleroderma.

Sera from 101 patients with progressive systemic scleroderma were analyzed for circulating aminopropeptides of type III collagen using a radioimmunoassay which measures the intact and degraded forms (Fab assay). About 41% of the patients were found to have values above the normal range. A good correlation was observed between elevated levels of aminopropeptides and the degree of involvement of the skin and internal organs in the patients. Most patients (89%) with an active progression of the disease but not those in a stationary phase showed increased serum levels of aminopropeptides. Treatment with corticosteroids apparently normalized the levels of aminopropeptides. Only minor changes were observed with an antibody-based radioimmunoassay which measures primarily the intact form of the aminopropeptide.