Vitamin D deficiency, spontaneous fractures, and osteopenia in rheumatoid arthritis.

Spontaneous, undisplaced fractures occurred in the long bones of five patients with longstanding rheumatoid arthritis. The results of biochemical, radiological, and dietary investigations in these patients were compared with those in a larger group of elderly women with rheumatoid arthritis without fractures. A significant association between skeletal rarefaction, calcium x phosphate product, and vitamin-D intake was shown in the whole group. Bone biopsies were performed in three patients with fractures, and histological evidence of osteomalacia was found in two patients. Dietary vitamin-D deficiency seems to play an important role in causing both the fractures and the osteopenia of longstanding rheumatoid arthritis.