Glutaryl-CoA dehydrogenase (GCDH) deficiency causes glutaric aciduria type I (GA I), an inborn error of metabolism that is characterized clinically by dystonia and dyskinesia and pathologically by neural degeneration of the caudate and putamen. Studies of metabolite excretion allowed us to categorize 43 GA I Spanish patients into two groups: group 1 (26 patients), those presenting with high excretion of both glutarate and 3-hydroxyglutarate, and group 2 (17 patients), those who might not be detected by routine urine organic acid analysis because glutarate might be normal and 3-hydroxyglutarate only slightly higher than controls. Single-strand conformation polymorphism (SSCP) screening and sequence analysis of the 11 exons and the corresponding intron boundaries of the GCDH gene allowed us to identify 13 novel and 10 previously described mutations. The most frequent mutations in group 1 were A293T and R402W with an allele frequency of 30% and 28%, respectively. These two mutations were also found in group 2, but always in heterozygosity, in particular in combination with mutations V400M or R227P. Interestingly, mutations V400M and R227P were only found in group 2, and at least one of these mutations was found in 11 of 15 unrelated alleles, accounting together for 53% of the mutant alleles in group 2. Therefore, it seems clear that two genetically and biochemically distinct groups of patients exist. The severity of the clinical phenotype seems to be closely linked to the development of encephalopathic crises rather than to residual enzyme activity or genotype. Comparison of GCDH protein with other acyl-CoA dehydrogenases (whose x-ray crystal structure has been determined) reveals that most of the mutations identified in GCDH protein seem to affect folding and tetramerization, as has been described for a number of mutations affecting mitochondrial ␤-oxidation acyl-CoA dehydrogenases.

The rate of onset of side effects was examined in 392 pediatric outpatients who received long-term monotherapy with phenobarbital (PB), primidone (PRM), phenytoin (PHT), carbamazepine (CBZ), or valproate (VPA) for epilepsy or febrile convulsions. The severity of side effects (based on need to alter treatment), the nature of each drug's most common side effects, and the doses and plasma levels of occurrence were recorded. Our results show that usually accepted therapeutic ranges are well tolerated. Indeed, although some form of side effect occurred in 50% of patients, treatment had to be changed in only 18% and the drug had to be stopped in only 7%. In decreasing order, the rates for side effects were PHT (71%) greater than PB (64%) greater than CBZ (43%) greater than VPA (43%) greater than PRM (29%). Serious side effects requiring withdrawal of treatment occurred at the following rates: PHT (10%) greater than VPA (8%) greater than PRM (8%) greater than PB (4%) greater than CBZ (3%). Among our patients, the best tolerated antiepileptic drug (AED) was CBZ, and the least tolerated was PHT. Behavioral disorders were most common with PB, neurologic disorders with PHT, digestive tract disorders with VPA, and gingival hyperplasia and hirsutism with PHT. Behavioral disorders involving excitement seen with PB and PRM occurred most commonly at low plasma levels. Behavioral disorders involving depression seen with PB and VPA, those involving excitement seen with PHT and VPA, and digestive disorders seen with VPA occurred particularly when plasma levels were high.

Epilepsy drug-resistance may depend on the metabolism of antiepileptic drugs (AEDs), transport to the epileptic focus and/or target sensitivity. Furthermore, drug response depends on multiple characteristics of the patient, the epilepsy, and the antiepileptic drugs used. We have investigated the association between polymorphisms related to antiepileptic drug metabolism (CYP2C9, CYP2C19, and UGT), transport (ABCB1), and targets (SCN1A) both in a crude analysis and after adjusting by clinical factors associated with drug-resistance, and stratifying by patient age or aetiology of epilepsy. Caucasian outpatients (N=289), children (N=80) and adolescent-adults (N=209), with idiopathic (N=69), cryptogenic (N=97) or symptomatic epilepsies (N=123) were selected when they had either drug-resistance (with at least four seizures over the previous year after treatment with more than three appropriate AEDs at appropriate doses) or drug responsiveness (without seizures for at least a year). Samples were genotyped by allelic discrimination using TaqMan probes. No significant association between polymorphisms and drug-resistance was found either in the crude analysis or in the adjusted analysis. However, adults with the ABCB1_3435TT or 2677TT genotypes had a lower risk of drug-resistance than those with the CC or the GG genotypes. Furthermore, patients with symptomatic epilepsies with the ABCB1_3435CT or TT genotypes had a lower risk of drug-resistance than those with the CC genotype. An opposite but insignificant tendency was found in children and in idiopathic epilepsies. Although replication studies will be needed to confirm our results, they suggest that stratification by patient age and by the aetiology of epilepsy could contribute to unmask the association between ABCB1 polymorphisms and drug-resistance of epilepsy.