PLATELET AND MONOCYTE VARIABLES IN HOMOCYSTINURIA DUE TO CYSTATHIONINE-BETA-SYNTHASE DEFICIENCY

To gain insight into the mechanisms responsible for enhanced thromboxa ne (TX) A(2) biosynthesis in homozygous homocystinuria due to cystathi onine-beta-synthase deficiency (CBSD), we measured a series of platele t and monocyte variables in 9 homozygous and 8 obligate heterozygous C BSD patients and evaluated their relationships to thromboxane formatio n, as reflected by urinary excretion of its major metabolite, 11-dehyd ro-TXB2 (TXM). Consistent with our previous data, homozygous CBSD pati ents 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 cr eatinine; p<0.05 vs. control subjects). All platelet and monocyte vari ables fell within the normal range in CBSD patients and none showed a correlation with TXM excretion (p always >0.05). Our results argue aga inst abnormalities of platelet and monocyte function being responsible for the abnormally high in vivo TXA(2) biosynthesis in homocystinuria due to CBSD.