Platelet and monocyte variables in homocystinuria due to cystathionine-beta-synthase deficiency

Abstract

To gain insight into the mechanisms responsible for enhanced thromboxane (TX) A2 biosynthesis in homozygous homocystinuria due to cystathionine-beta-synthase deficiency (CBSD), we measured a series of platelet and monocyte variables in 9 homozygous and 8 obligate heterozygous CBSD patients and evaluated their relationships to thromboxane formation, as reflected by urinary excretion of its major metabolite, 11-dehydro-TXB2 (TXM). Consistent with our previous data, homozygous CBSD patients showed abnormally high TXM excretion (1175 +/- 236 pg/mg creatinine vs. 284 +/- 39 in control subjects; p < 0.001). Significantly higher TXM excretion was also found in obligate heterozygotes (755 +/- 450 pg/mg creatinine; p < 0.05 vs. control subjects). All platelet and monocyte variables fell within the normal range in CBSD patients and none showed a correlation with TXM excretion (p always > 0.05). Our results argue against abnormalities of platelet and monocyte function being responsible for the abnormally high in vivo TXA2 biosynthesis in homocystinuria due to CBSD.