HyperCKemia and rhabdomyolysis in the neuroleptic malignant and serotonin syndromes: A literature review.

Neuroleptic malignant syndrome and serotonin syndrome are two syndromes whose molecular bases remain poorly understood. The phenotypes of both syndromes overlap with other syndromes that have a clear genetic background, in particular RYR1-related malignant hyperthermia. Through a literature review, performed according to the PRISMA guidelines, we aimed to report the clinical features of both syndromes, and the results of genetic testing performed. 10 case series and 99 case reports were included, comprising 134 patients. A male predominance of 58% was found. The median age was 35 (range 4-84) years. Eight patients experienced recurrent episodes of rhabdomyolysis. Genetic analysis was performed in eleven patients (8%), revealing four RYR1 variants, three likely benign (p.Asp849Asn, p.Arg4645Gln, p.Arg4645Gln) and one variant of uncertain significance (p.Ala612Thr). This review underlines that a subset of patients with neuroleptic malignant syndrome and serotonin syndrome develop recurrent episodes of rhabdomyolysis. This recurrent pattern suggests a possible underlying (genetic) susceptibility. However, the genetic background of neuroleptic malignant syndrome and serotonin syndrome has only been investigated to a very limited degree so far. The increasing availability of next generation sequencing offers an opportunity to identify potentially associated genetic backgrounds, especially in patients with recurrent episodes or a positive family history.

Histaminergic gene polymorphisms associated with sedation in clozapine-treated patients.

Sedation is a common adverse effect of clozapine treatment, which may be partly related to clozapine binding to histamine receptors in the central nervous system. The objective of this study was to investigate whether single nucleotide polymorphisms (SNPs) in the histaminergic system are associated with sedation in clozapine-treated patients. The study population comprised 237 clozapine-treated, Finnish, Caucasian patients that were diagnosed with schizophrenia and 176 were genotyped using Illumina HumanCoreExome-12 BeadChip. Sedation levels were assessed using self-rating questions from the Liverpool University Neuroleptic Side Effect Rating Scale (LUNSERS). The relationships between 55 different SNPs in the histaminergic system and adverse sedation effects were examined. SNPs were analyzed separately, and in groups, to formulate a genetic risk score (GRS). A permutation test was performed to avoid type I errors. Eight linked SNPs (r2 = 1) in the HNMT gene were also associated with sedation according to the GLM, adjusted for age, gender and BMI (false-discovery-rate-adjusted p = 0.013). An association on a trend level between a GRS of four different SNPs (recessive histamine N-methyltransferase HNMT rs2737385, additive histamine receptor H1 rs1552498, dominant HRH1 rs17034063 and recessive amine oxidase, copper containing 1 AOC1 rs6977381) and sedation was found (permuted p-value = 0.066) in a generalized linear model (GLM) incorporating age, gender and body mass index (BMI; adjusted R2 = 0.22). Polymorphisms in genes encoding histamine receptors or enzymes related to histamine metabolism may explain individual variation in sedative effects experienced during clozapine treatment.

Neuroleptic malignant syndrome in an adolescent with CYP2D6 deficiency.

We describe a patient with dystonia and psychotic symptoms treated with standard doses of antipsychotics, who developed neuroleptic malignant syndrome (NMS). A 16-year-old male with a history of misuse of dextromethorphan and pseudoephedrine for recreational purpose presented with dystonia and a psychotic episode. Following continuous treatment with olanzapine (10 mg/day), repeated injections of levomepromazine (37.5 mg/day), and a single injection of haloperidol (2.5 mg), the patient developed NMS. Muscular rigidity, fever (up to 41 °C), hypotension (100/70 mmHg), tachycardia (120 beats per minute), tachypnea (26 breaths per minute), elevated leukocyte count (up to 16.6 × 10(3)/µL), and elevated serum creatinine phosphokinase (CPK) (up to 15,255 U/L) were observed. A diagnosis of NMS was made according to the DSM-IV TR criteria. Genotyping revealed that he was homozygous for a non-functional CYP2D6*4 allele. The case highlights the importance of therapeutic drug monitoring in identification and differentiation of drug-induced effects in psychiatric disorder to prevent NMS and its complications. In addition, genotyping of CYP2D6 might be considered in patients with symptoms suggestive of drug toxicity who are treated with neuroleptics metabolized via the CYP2D6 pathway, as carriage of one or more non-functional alleles may increase the risk for adverse reactions, such as NMS.

Síndrome neuroléptica maligna / Neuroleptic malignant syndrome

JUSTIFICATIVA E OBJETIVOS: A síndrome neuroléptica maligna (SNM) apresenta incidência muito variável na população, sem haver uma associação significativa com fatores de risco sociais, étnicos ou sazonais. Em 90% dos casos o quadro clínico se completa nas primeiras quatro a oito horas, após os primeiros sintomas, podendo ter evolução grave e fatal se a conduta não for feita de forma correta, tornando seu conhecimento de extrema valia. O objetivo deste estudo foi rever os fatores de risco, quadro clínico, fisiopatogenia, diagnóstico diferencial e tratamento da SNM para melhor qualidade de vida dos pacientes. CONTEÚDO: Utilizou-se o portal Capes como base da pesquisa em periódicos que abordassem o tema, utilizando-se artigos de revisão, excluindo-se relatos de caso, as palavras-chaves usadas durante a busca foram: Síndrome Neuroléptica Maligna. Seu conhecimento se torna importante ao ter um diagnóstico de exclusão, que feito em um curto espaço de tempo possui significância na evolução do quadro. CONCLUSÃO: A falta de conhecimento sobre a SNM significa um risco potencial importante ao paciente, inclusive podendo levá-lo ao óbito, além de haver uma evolução rápida. Por ser uma complicação idiossincrática, sua importância é ainda maior. Entretanto com o cuidado correto a reversão do quadro é possível.

BACKGROUND AND OBJECTIVES: Neuroleptic malignant syndrome (NMS) has a highly variable incidence in the population without a significant association with social, ethnic or seasonal risk factors. In 90% of cases, the clinical picture is complete in the first 4 to 8 hours after the first symptoms; evolution may be serious and fatal if the treatment is not correct; thus, its knowledge is invaluable. The objective of this study was to review risk factors, clinical features, pathophysiology, differential diagnosis and treatment of the NMS to improve patients' quality of life. CONTENTS: CAPES website was used as a basis for the research in journals that addressed this issue, using review articles and excluding case reports; the key words used during the search were: Neuroleptic Malignant Syndrome. The knowledge of this syndrome becomes important when we make an exclusion diagnosis, which has significance in the evolution of the clinical picture when made in a short time. CONCLUSION: The lack of knowledge about NMS implies potential risk for the patient, may lead to fast progression and even to death. Because it is an idiosyncratic complication, its importance is even greater. However, with the right care, there is a possibility of clinical picture reversal.

Ecstacy-induced delayed rhabdomyolysis and neuroleptic malignant syndrome in a patient with a novel variant in the ryanodine receptor type 1 gene.

We present the case of a 20-year-old woman who developed rhabdomyolysis, disseminated intravascular coagulopathy and multi-organ failure induced by ecstasy. Following initial improvement, she developed delayed rhabdomyolysis then haloperidol-induced neuroleptic malignant syndrome, which was treated with a total of 50 mg.kg(-1) dantrolene. Subsequent genetic testing revealed a novel potentially pathogenic variant in the ryanodine receptor type 1 gene. However, caffeine-halothane contracture testing of the patient's mother who carried the same gene variant was negative for malignant hyperthermia.

A case study: neuroleptic malignant syndrome with risperidone and CYP2D6 gene variation.

We present a schizophrenic patient who experienced neuroleptic malignant syndrome with risperidone treatment due to variants of the CYP2D6 gene with reduced function. Clinicians need to be aware of this potential complication.

Functional SNPs in genes encoding the 5-HT2A receptor modify the affinity and potency of several atypical antipsychotic drugs.

Atypical antipsychotic drugs (AADs) are the standard treatment for both the acute and long-term management of schizophrenia and an augmentation to mood stabilizers for bipolar disorder (BD). Yet many individuals who take AADs do not fully respond to them, while others experience side effects that include weight gain and metabolic disorder. This in vitro pharmacogenetic study examined whether allelic variants in the 5-hydroxytryptamine (HT)(2A) receptor alter the in vitro pharmacology of six AADs (clozapine, olanzapine, risperidone, quetiapine, ziprasidone, and aripiprazole). We selected 4 functional single-nucleotide polymorphisms (SNPs) for investigation (Thr25Asn, Ile197Val, Ala447Val, and His452Tyr), conducted site-directed mutagenesis studies to induce variants into human HEK-293 cell lines, and screened allelic variants for their effects on 5-HT( 2A) receptors in the cell lines. We conducted numerous binding assays and fluorescence-based assay system (FLEX station) experiments using the six AADs. Our results indicated that three polymorphic 5-HT(2A) receptors (Ile197Val, Ala447Val, and His452Tyr) exhibited statistically significant, though modest, changes in atypical antipsychotic affinity. In addition, three polymorphic receptors (Thr25Asn, Ile197Val, and His452Try) altered AAD potency. Our findings support in vivo evidence that functional SNPs in genes encoding neuroreceptor drug targets could explain interindividual differences in AAD drug response and tolerability. We suggest that more in vivo pharmacogenetic studies of well-characterized patients who are prescribed AADs be indicated. Future pharmacogenetic studies of well-characterized patients will likely involve tagging SNPs and the use of haplotypes related to other genes encoding neuroreceptor drug targets.

The role of CYP2D6 and TaqI A polymorphisms in malignant neuroleptic syndrome: two case reports with three episodes.

Malignant neuroleptic syndrome (MNS) is a serious and potentially fatal side-effect of neuroleptic treatment. Beside antipsychotic drugs, other psychotropic drugs such as antidepressants and lithium carbonate can cause this life threatening side-effect. Underlying mechanism of this side-effect is still unknown and debated. So far some risk factors have been identified, with clinical observations and recent pharmacogenetic research suggesting (with inconsistent findings) correlation between genetic mechanisms and predisposition to MNS. Polymorphisms of CYP2D6 enzyme through which most psychotropic drugs are metabolized and TaqIA DRD2 which is target for antipsychotic drugs could be the link between pharmacogenetic factors and potential for development of MNS. In this paper we present two case reports with clinical presentation of three consecutive MNS. One patient developed MNS while he was taking combination of drugs: first time haloperidol, promazine and fluphenazine, second time fluphenazine and perazine and third time clozapine, promazine and valproic acid consecutively. The other patient developed MNS while taking following combination of drugs: first time haloperidol and lithium carbonate, second time risperidone and third time clozapine consecutively. Pharmacogenetic analysis for CYP2D6 and TaqI A DRD2 polymorphisms for both patients was done. Genotypisation of CYP2D6*1*3*4*5*6 in both patients showed no evidence of poor metabolizer phenotype. On the other hand, first patient was heterozygous for CYP2D6*4 (genotype *1/*4). CYP2D6 polymorphisms could have clinical significance because may lead to toxicity and unwanted side-effects in standard usual antipsychotic dose ranges. Analysis Taql A DRD2 polymorphism for first patient showed that he is heterozygous for A1 allele (genotype A1A2) which is commonly associated with predisposition to MNS. According to our literature three consecutive MNS are rarely described, and incidence of MNS generally is too low to perform clinical research. Many patophysiological mechanisms may probably underlie this complex and potentially fatal syndrome, still unknown etiology. But, genetic mechanisms could be significant. Further pharmacogenetic research, findings and analysis in patients who develop single or repeated MNS are strongly recommended. In long term, pharmacogenetic analysis, implemented in daily clinical practice, could help in prevention of this extremely serious side-effect.

Possible contribution of XYY syndrome to neuroleptic malignant syndrome in a child receiving quetiapine.

PURPOSE: A case of early neuroleptic malignant syndrome (NMS) in a child with XYY syndrome after three weeks of quetiapine therapy is reported. SUMMARY: A four-year-old, 23-kg boy with a history of oppositional defiant disorder, mood disorder, and XYY syndrome was brought to the emergency care center (ECC) for evaluation secondary to somnolence, gait disturbances, and altered mental status. Three weeks prior, he was started on a daily oral dose of quetiapine 25 mg; this was adjusted upward to 400 mg daily. He had been experiencing episodes of severe confusion, somnolence, and extreme agitation. He was also ataxic and unbalanced on his feet. Upon evaluation at the ECC, he was found to have an elevated creatine kinase (CK) concentration, as well as elevated CK-MB and CK-MM levels, both of which were indicative of skeletal muscle damage. He was slightly diaphoretic and displayed mild rigidity accompanied by varying degrees of agitation and confusion. The diagnosis of NMS secondary to quetiapine therapy was made. Quetiapine was discontinued, and the patient was admitted for observation. His symptoms steadily resolved over the course of his hospital stay, and his total CK levels, as well as CK isoenzyme levels, fell over the course of observation. Quetiapine was not restarted at discharge, and no new medications were prescribed. CONCLUSION: A four-year-old boy with XYY syndrome developed signs and symptoms consistent with early NMS after three weeks of quetiapine therapy. High-dose quetiapine, along with possible baseline liver dysfunction secondary to XYY syndrome, may have contributed to the development of NMS in this patient, which resolved after the discontinuation of quetiapine.

Postmortem molecular screening for mutations in ryanodine receptor type 1 (RYR1) gene in psychiatric patients suspected of having died of neuroleptic malignant syndrome.

Postmortem diagnosis of neuroleptic malignant syndrome (NMS) is difficult to perform, because the clinical symptoms just before death are not usually available. Malignant hyperthermia (MH) is a catastrophic, life-threatening hypermetabolic syndrome triggered by certain anesthetics. Ryanodine receptor type 1 (RYR1) gene mutations are known to be involved in susceptibility to MH. Similarities in clinical features, such as elevated body temperature, between NMS and MH have led to the suggestion that NMS is a neurogenic form of MH. In this study, we analyzed possible mutations of the RYR1 gene in 11 psychiatric patients suspected at autopsy to have died of NMS. All cases were suspected of having elevated body temperature at death, and their causes of death could not be determined by autopsy examinations. Two mutations (R4645Q and A612T) in the RYR1 gene were identified. The R4645Q mutation has previously been reported in MH patients, but five heterozygous mutations were also found in 400 Japanese control alleles. The other mutation was novel, and was not found in the same control alleles. The results of this study provide the first successful identification of RYR1 mutations in psychiatric patients suspected at autopsy of having died of NMS. However, the association between RYR1 gene mutations and cause of death in psychiatric patients suspected of dying of NMS remains unclear.

Effects of CYP2D6 polymorphisms on neuroleptic malignant syndrome.

OBJECTIVE: Neuroleptic malignant syndrome (NMS) is one of the most serious adverse reactions to antipsychotic medications. We accumulated data on Japanese NMS patients and, in a study designed to examine the effects of drug metabolism on the occurrence of NMS, tested the possibility of association between NMS and CYP2D6 polymorphisms. METHODS: We studied 53 patients who had experienced NMS and 112 healthy individuals. We determined what drugs the patients with NMS had been given and retrospectively identified candidates for drugs causing NMS. We screened the prevalence of CYP2D6 genotypes using polymerase chain reaction and restriction fragment length polymorphism analyses. RESULTS: The prevalence of *5 alleles in the group of all patients with NMS was higher than that in the controls, though this difference was not statistically significant (10.4% vs. 5.4%; P = 0.107; odds ratio (OR) 2.05; 95% confidence interval (CI) 0.87-4.80). No association was found between the frequency of *10 alleles and the occurrence of NMS. We found *4 and duplicated alleles in only one patient each among the patients with NMS. A total of 29 patients appeared to have developed NMS as a result of having taking CYP2D6 substrates. The prevalence of *5 alleles in these 29 patient was significantly higher than that in the controls (15.5% vs. 5.4%; P = 0.020; OR 3.25; 95% CI 1.30-8.13). CONCLUSION: Our findings suggest that the CYP2D6*5 allele is likely to affect vulnerability to development of NMS.

CYP2D6 gene deletion allele in patients with neuroleptic malignant syndrome: preliminary report.

Neuroleptic malignant syndrome (NMS) is a potentially fatal adverse reaction to psychopharmacologic treatment. Reported herein are two NMS patients with schizophrenia who were found to possess a CYP2D6 gene deletion allele (CYP2D6*5). The deletion results in decreased CYP2D6 activity, possibly leading to drug accumulation. Both patients with NMS had been treated with neuroleptics, including CYP2D6 substrates. Polymerase chain reaction (PCR) followed by restriction fragment length polymorphism analyses and long PCR were performed to detect CYP2D6 genotype. One patient was found to possess *5/*10; the other had a *1/*5 genotype. The present preliminary report suggests that pharmacokinetic factors cannot be excluded and the CYP2D6 polymorphism is possibly associated with the etiology of NMS.

Family history of primary movement disorders as a predictor for neuroleptic-induced extrapyramidal symptoms.

BACKGROUND: A genetic susceptibility to extrapyramidal symptoms caused by treatment with neuroleptic medication has been suggested. AIMS: To identify predictor variables for neuroleptic-induced extrapyramidal symptoms, particularly considering family history of primary movement disorders. METHOD: We investigated 100 in-patients receiving a stable neuroleptic medication with regard to occurrence of extrapyramidal symptoms, drug history and detailed family history of primary movement disorders. RESULTS: Step-wise logistic regression analysis revealed that a positive family history was a significant predictor for lifetime prevalence of extrapyramidal symptoms, including reported and currently observed symptoms. The duration of exposure to neuroleptic medication and age were further predictors. CONCLUSIONS: Our findings underline the notion of genetic susceptibility for secondary extrapyramidal symptoms and suggest possible shared genetic factors in primary and secondary movement disorders as well as psychotic disorders.

Association in Japanese patients between neuroleptic malignant syndrome and functional polymorphisms of the dopamine D(2) receptor gene.

A genetic predisposition to the development of neuroleptic malignant syndrome (NMS) has been suggested by clinical studies. Although the molecular basis of NMS is unclear, a dopaminergic blockade mechanism has been considered the main cause. We therefore investigated the association between NMS and three functional polymorphisms of the dopamine D(2) receptor (DRD(2)) gene: TaqI A, -141C Ins/Del, and Ser311Cys. Subjects included 32 Japanese patients, previously diagnosed with NMS, and 132 schizophrenic patients treated with neuroleptics without occurrence of NMS. Polymerase chain reaction and restriction fragment length polymorphism analyses were performed to determine each genotype. We found significant differences in genotypic and allelic frequencies of the -141C Ins/Del polymorphism between patients with and without NMS. The -141C Del allele was significantly more frequent in the NMS group (23.4 vs 11.7%, P=0.026). Similarly, the proportion of -141C Del allele carriers was significantly higher in the NMS group (40.6 vs 20.5%, P=0.022). No significant differences between the two groups were seen for allelic and genotypic frequencies of the TaqI A and Ser311Cys polymorphisms. This result suggests that the -141C Ins/Del polymorphism is likely to predispose toward the development of NMS, probably together with other unidentified factors.