Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nonketotic hyperglycinaemia (NKH) is an inborn error of the glycine cleavage system resulting in seizures and mental retardation. Two prior reports noted an anticonvulsant effect from high-dose dextromethorphan (DM) in this disorder, although the two reported patients demonstrated widely disparate DM requirements and drug levels. We report two children with NKH who also demonstrated disparate and variable DM metabolism which markedly influenced the dose-concentration-response relationship. Levels of DM and its primary metabolite dextrorphan (DX) were utilized to guide DM therapy and exhibited patterns reflective of the extensive and poor metabolizer phenotypes for CYP2D6, the cytochrome P450 isoform responsible for DM metabolism. In the patient who appeared to represent the extensive metabolizer (EM) phenotype, treatment with the non-specific cytochrome P450 inhibitor cimetidine was required to reduce biotransformation of DM to DX and, thus, to increase DM plasma concentrations. In the patient with the apparent poor metabolizer (PM) phenotype, a change in the DM preparation to a sustained-release form and increase in the dosing interval was required to lower DM plasma concentrations. These cases demonstrate the importance of CYP2D6 phenotype in providing safe and effective DM therapy to patients with NKH.
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PMID:Dextromethorphan in nonketotic hyperglycinaemia: metabolic variation confounds the dose-response relationship. 906 64

(1) Severe myoclonic epilepsy of infancy (Dravet's syndrome) is associated with multiple seizures and progressive onset of mental retardation. Available antiepileptics (valproic acid and clonazepam/clobazam) are only partially effective, even when used in combination. (2) Stiripentol is intended to be added to the valproate + clobazam combination when the latter is ineffective. (3) In a two-month double-blind trial, 9 of 21 infants remained seizure-free when stiripentol was added to the valproate-clobazam combination, whereas all 20 infants receiving a placebo instead of stiripentol continued to have seizures. (4) Two follow-up studies lasting two and three years and involving 37 and 46 children showed that about 20% of patients had a major benefit (fewer seizures) when stiripentol was added to inadequately effective valproate-clobazam combination therapy. The possible impact of stiripentol on psychomotor development is unknown. Stiripentol was only moderately effective in adolescents. (5) Stiripentol has common and sometimes serious adverse effects such as loss of appetite (with ensuing weight loss), drowsiness and insomnia. Stiripentol inhibits several cytochrome P450 isoenzymes, including CYP 3A4, creating a high risk of interactions, especially with co-administered antiepileptics. (6) The stiripentol dose strengths currently available in France are unsuitable for infants weighing less than 10 kg. (7) In practice, given the severity of this type of myoclonic epilepsy of infancy, the addition of stiripentol to ongoing but ineffective valproate-clobazam combination therapy is justified, even though the treatment is somewhat difficult to manage and has not yet been fully evaluated.
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PMID:Stiripentol: new preparation. Severe myoclonic epilepsy of infancy: promising. 1587 42

Fragile X mental retardation 1 (FMR1) premutation associated phenotypes have been explored extensively since the molecular mechanism emerged involving elevated FMR1 messenger ribonucleic acid (mRNA) levels. Lowered fragile X mental retardation protein (FMRP) can also occur which may have an additive effect to the high levels of mRNA leading to neurodevelopmental problems and psychopathology. This paper was aimed to review psychosis and catatonia in premutation carriers, express the role of elevated FMR1 mRNA and lowered FMRP in the phenotype of carriers and present a case of psychosis and catatonia in a carrier. This case also demonstrates additional genetic and environmental factors which may also affect the phenotype. We review the literature and report an exemplary case of a 25 year old male premutation carrier with elevated FMR1 mRNA, low FMRP, a cytochrome P450 family 2 subfamily D polypeptide 6 (CYP2D6)*2xN mutation and a perinatal insult. This patient developed an autism spectrum disorder, psychosis, catatonia with subsequent cognitive decline after electro-convulsive therapy (ECT) for his catatonia. He had a premutation of 72 CGG repeat in FMR1, FMR1 mRNA level that was over 2.4 times normal and FMRP level at 18% of normal, and additionally, a CYP2D6 allelic variant which leads to ultrarapid metabolism (UM) of medication. There is an overlapping pathophysiological mechanism of catatonia and fragile X-associated premutation phenotypes including autism and psychosis. This case demonstrates the shared phenotype and the overlap of the pathophysiological mechanisms that can influence the intervention. Multiple genetic and environmental hits can lead to more significant involvement in premutation carriers.
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PMID:Psychosis and catatonia in fragile X: Case report and literature review. 2636 65