Low levels of serum type III procollagen aminoterminal propeptide confirmed type III collagen deficiency in patients without typical clinical symptoms of Ehlers-Danlos type IV.

Biochemical analysis of skin samples revealed that the content of type III collagen was greatly reduced in several subjects with joint hypermobility, stretchability and bruisability of skin. When cultured dermal fibroblasts were found to secrete decreased amounts of type III procollagen into medium (about 30-45% the normal amount) and serum type III procollagen aminopropeptide levels were significantly lower than normal values (P less than 0.001). The abnormalities in type III procollagen are in keeping with Ehlers-Danlos type IV although the clinical findings in our patients are not normally associated with this disorder. The results illustrate the clinical heterogeneity of Ehlers-Danlos type IV and the importance of biochemical analysis, such as determination of type III procollagen aminopropeptide levels, to check type III collagen metabolism especially if there is no family history and if correct diagnosis is not reliable by clinical examination alone.