Metaplastic bone formation in the subcutaneous nodule of a patient with mixed connective tissue disease.

Cutaneous ossification is a rare phenomenon in collagen diseases, despite the rather frequent occurrence in these diseases of dystrophic calcinosis. We observed metaplastic woven bone formation associated with calcification in biopsy material obtained from a 49-year-old woman suffering from mixed connective tissue disease together with multiple subcutaneous indurations. This is the first case of the presence of metaplastic bone formation in a patient with mixed connective tissue disease.