Platelet function and morphology in homocystinuria

Abstract

Platelet-function tests and morphological investigations by electron microscopy were performed in 8 patients with homocystinuria due to cystathionine synthase deficiency. In 3 patients, all pyridoxine-responders, the collagen-, ADP- and adrenalin-induced platelet aggregation was decreased before treatment; it returned to normal during treatment when homocystine disappeared from plasma. The platelet factor 3 availability, decreased before treatment, also became normal when pyridoxine was administered. The open canalicular system occupied 7.2 per cent of the total area of the platelets before treatment and decreased to 4.5 per cent 3 months later; the α-granules, on the other hand, increased from 7.2 to 11.1 per cent. Functional and morphological studies in the 5 patients already under treatment showed normal results. We conclude that the platelet alterations in untreated patients result from their refractory stage after a release reaction has taken place; the latter may be caused by the homocystine-induced endothelial lesions. In adequately treated patients, our data suggest that no additional administration of inhibitors of platelet aggregation is necessary.