Homocystinuria (cystathionine synthase deficiency). Results of treatment in late-diagnosed patients.

The clinical outcome in 12 late-diagnosed patients with homocystinuria is reported. Three children died: all were mentally damaged and were never treated effectively. Eight children have been treated with pyridoxine--or with a low-methionine diet with supplemental L-cystine--for 2 to 9 years. Follow-up of these patients shows a striking improvement in behaviour and intellectual development in close correlation to the biochemical normalisation. No thromboembolic episodes occurred in adequately treated patients. However, in one child thrombosis of the retinal artery developed during dietary failure. In another patient the characteristic symptoms of an endangiitis obliterans completely disappeared. Both the reversibility and the improvement of some of the main sequelae in homocystinuria emphasize the need to treat all patients, regardless of their age at diagnosis.