Severe subcutaneous calcification in the 'CREST' syndrome: evidence of high turnover of calcific deposits.

Four patients with mild CREST syndrome and extensive subcutaneous calcification have been studied over a 5-year period. There was no correlation between mineral deposition and other features of the disease and no obvious clinical or metabolic cause of the calcification. Mineral deposits, identified as crystalline carbonated apatite, were very labile. A clear pattern of radiographic evolution was apparent. Bone scans showed a higher uptake of isotope in new, developing deposits than in older lesions. Spontaneous formation and disappearance of adjacent deposits occurred in some patients. Loss of mineral could not be explained by extrusion through the skin.