We examined the influence of combined genotypes on interindividual variability in warfarin dose-response. In 100 anticoagulated patients we quantified the effects of polymorphisms in: CYP2C9, VKORC1, calumenin (CALU), gamma-glutamyl carboxylase (GGCX) and microsomal epoxide hydrolase (EPHX1) on warfarin dose requirements. The G(1542)C VKORC1 polymorphism was associated with decreased warfarin doses in the hetero- and homozygous mutant patients (21% and 50% lower, respectively; p < 0.0001). Warfarin daily dose was predominantly determined by VKORC1 and CYP2C9 genotypes (partial r(2) = 0.21; 0.20, respectively). Together with age and body weight, these two genotypes explained 63% of the dose variance. A single patient, homozygous for G(11)A CALU mutant allele, required an exceptionally high warfarin dose (20 mg/day) and the prevalence of heterozygous (11)A allele carriers in the upper 10(th) dose percentile was significantly higher (0.27 vs. 0.18, p < 0.02). Combined genotype analysis revealed that CYP2C9 andVKORC1 wild type and CALU mutant patients required the highest warfarin doses (7.8 +/- 1.5mg/day; n = 9) as compared to the CYP2C9 and VKORC1 mutant and CALU wild type genotypes (2.8 +/- 0.3 mg/day; n = 18; p < 0.01). The odds ratio for doses <3mg/day was 5.9 (1.9-18.4) for this genotype. Compound genetic profiles comprising VKORC1, CALU and CYP2C9 improve categorization of individual warfarin dose requirements in more than 25% of patients at steady-state anticoagulation.

CYP2C9 and VKORC1 genetic variants are associated with low and intermediate warfarin dose requirements, but markers of high doses are less well characterized. We analyzed the VKORC1 coding sequence and known CYP2C9 and VKORC1 polymorphisms in 15 selected warfarin-resistant (dose, 80 to 185 mg/wk) and 8 warfarinsensitive patients (7 to 13 mg/wk) and 99 unselected controls (8 to 105 mg/wk). We identified a coding VKORC1 Asp36Tyr polymorphism in 7 of 15 resistant compared with 0 of 8 sensitive patients (P ‫؍‬ .026) Carriers of Asp36Tyr in the control group (8 of 99) required significantly higher warfarin doses of 80.9 ؎ 10.1 mg/wk compared with 42.7 ؎ 7.5 mg/wk in noncarriers (F ‫؍‬ 9.79, P ‫؍‬ .002). Asp36Tyr was significantly associated with doses of more than 70 mg/wk (odds ratio, 13.0; 95% confidence limit, 1.3 to 124.2), while doses of 20 to 70 mg/wk were associated with Asp36Tyr (partial r 2 ‫؍‬ .11; P ‫؍‬ .004), CYP2C9*2 and *3 (r 2 ‫؍‬ .08; P ‫؍‬ .01), and VKORC1*2 and *3 markers (r 2 ‫؍‬ .05; P ‫؍‬ .05). All Asp36Tyr carriers also had VKORC1*1 tag-single nucleotide polymorphisms (tag-SNPs) indicating a new haplotype. Asp36Tyr was common in Jewish ethnic groups of Ethiopian (15%) and Ashkenazi (4%) origin. We suggest that Asp36Tyr is a new marker of the high end of the warfarin dosing range. IntroductionReduced warfarin dose requirements are dictated by the CYP2C9*2 and *3 genetic variants due to decreased S-warfarin metabolic clearance and by the VKORC1*2 haplotype (or H1 and H2) with decreased VKORC1 activity and lower ambient reduced vitamin K levels. [1][2][3][4][5][6][7] Variants affecting the intermediate range of warfarin doses include the VKORC1*3 and *4 (or H7, H8, and H9) haplotypes. [4][5] At the other end of the dose spectrum, several rare VKORC1 mutations have been described, including the original report on 4 distinct mutations in warfarin-resistant individuals, 8 a rare Val66Met mutation associated with high warfarin doses, 9-10 and an Asp36Tyr mutation described in 2 patients with doses of 40 to 50 mg/wk 11 However, genetic effects on the highest warfarin doses (more than 80 mg/wk), which are met in clinical practice, have been less well characterized. In an attempt to identify novel markers of warfarin resistance, we performed sequence analysis of all the coding exons in the VKORC1 gene in a selected group of warfarin-resistant and warfarin-sensitive patients, including an analysis of known polymorphisms in CYP2C9 and VKORC1. We validated our findings in a series of unselected warfarin-treated patients described in our previous studies. [12][13] Patients, materials, and methods Patients were at stable anticoagulation (therapeutic international normalized ratio [INR] in 4 clinic visits). Resistant patients were defined by warfarin dose requirements of at least 80 mg/wk in the absence of known dose-increasing factors and sensitive patients by doses of 13 mg/wk or less.The controls were 99 previously described patients recruited as an unselected consecutive series. We recorded patient sex, a...

Summary Purpose:  Rett syndrome (RTT), an X‐linked, dominant neurodevelopmental disorder caused by mutations in the methyl‐CpG‐binding protein 2 (MECP2) gene, presents with acquired microcephaly, autistic regression, hand usage loss, and stereotypies. Epilepsy is frequent and has been reported to correlate with mutation type, general disease severity, and BDNF polymorphism. Our purpose was a comprehensive description of epilepsy features and course in RTT. Methods:  Retrospective review of charts and electroencephalography (EEG) studies in 97 patients with RTT. Results:  Seventy‐two percent of patients had epilepsy, appearing at a median age of 3 years. According to age of onset, we divided patients into three groups: 6 with early epileptic variant (0–1 year), 42 with early epilepsy (1–5 years), and 20 with late epilepsy (after 5 years). Early epileptic variant had severe seizure types in the first year of life, followed by a typical RTT picture; all were MECP2 negative. Early epilepsy and late epilepsy groups were similar with respect to Rett‐related symptoms, but seizures were better controlled in the second group (p < 0.05). Epileptiform activity appeared earlier and was more confluent in the early epilepsy group, including nine patients with electrical status epilepticus during sleep (ESES) versus one in the late epilepsy group (p < 0.05). No correlation was found between epilepsy onset or severity and genotype. BDNF val/met polymorphism correlated with earlier onset of seizures (p < 0.05). Discussion:  Epilepsy appears earlier than described previously, frequently during the regression stage. Early age of onset predicts a more severe course of seizures. ESES is common among those with early onset epilepsy. BDNF polymorphism was the only genetic correlate with seizure onset, whereas MECP2 mutation type and location did not influence epilepsy.

Variant mEH T 612 C genotypes are associated with warfarin doses of greater than 50 mg/wk beyond the effect of CYP2C9.