Fibrodysplasia ossificans progressiva. Biochemical changes in blood serum, urine, skin, bone, and ectopic ossification.

Increased urinary output of total hydroxyproline, hydroxylysine and uronic acid was found in two patients suffering from fibrodysplasia ossificans progressiva. Before treatment of one of the patients, the high molecular weight peptide fraction deriving from newly synthesised collagen was particularly increased. Treatment with disodium etidronate (diphosphonate) reduced the values. The urinary values of sodium, potassium and calcium were also depressed during treatment, and, in both patients, serum phosphate was high, while serum calcium was normal. The hydroxyproline and hydroxylysine contents in skin and bone of FOP patients did not differ from controls, while ectopic ossifications showed a considerable increase in hydroxylysine in relation to normal bone.