tions, including recurrent spontane-ous abortions, intrauterine growth retardation, and neonatal demise, tested positive for the C20221T or C20209T mutation (6). In summary, all 3 mutations (C20209T, A20218G, and C20221T) give LightCycler melt-ing curves that are clearly distin-guishable from those obtained in wild-type or G20210A samples. Therefore, the conscientious hints in-cluded in the factor II assay package insert noting that these rare muta-tions will possibly lead to a false-positive result might be exaggerated. Furthermore, it is tempting to specu-late that all 3 variants are rare and possibly have different frequencies in different ethnic groups. Because the patient identified in our laboratory as carrying the A20218G transition also tested het-erozygous for factor V Leiden (G1691A) and the methylenetetrahy-drofolate reductase (C677T) muta-tion, the clinical significance of this mutation is currently unknown. However, based on the knowledge that the G20210A substitution repre-sents in vitro a gain-of-function mu-tation causing mRNA accumulation and increased protein synthesis (7), creates in vitro but not in vivo a more effective polyadenylation site and cleavage site (7–9), and is proposed to be associated with different mRNA structures leading to abnor-mal mRNA function (9), it will be worthwhile to initiate additional studies to estimate the impact of this genetic variant on risk assessment for thrombotic events and adverse pregnancy outcomes
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