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

Department of Clinical and Experimental Medicine, University of Naples, Federico, Italy.

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.

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