Thr105Ile (rs11558538) polymorphism in the histamine N-methyltransferase (HNMT) gene and risk for Parkinson disease A PRISMA-compliant systematic review and meta-analysis

Background/aims: Several neuropathological, biochemical, and pharmacological data suggested a possible role of histamine in the etiopathogenesis of Parkinson disease (PD). The single nucleotide polymorphism (SNP) rs11558538 in the histamine Nmethyltransferase (HNMT) gene has been associated with the risk of developing PD by several studies but not by some others. We carried out a systematic review that included all the studies published on PD risk related to the rs11558538 SNP, and we conducted a meta-analysis following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Methods: We used several databases to perform the systematic review, the software Meta-DiSc 1.1.1 to perform the metaanalysis of the eligible studies, and the Q-statistic to test heterogeneity between studies. Results: The meta-analysis included 4 eligible case–control association studies for the HNMT rs11558538 SNP and the risk for PD (2108 patients, 2158 controls). The frequency of the minor allele positivity showed a statistically significant association with a decreased risk for PD, both in the total series and in Caucasians. Although homozygosity for the minor allele did not reach statistical significance, the test for trend indicates the occurrence of a gene–dose effect. Global diagnostic odds ratios (95% confidence intervals) for rs11558538T were 0.61 (0.46–0.81) for the total group, and 0.63 (0.45–0.88) for Caucasian patients. Conclusion: The present meta-analysis confirms published evidence suggesting that the HNMT rs11558538 minor allele is related to a reduced risk of developing PD.Trabajo financiado por: Instituto de Salud Carlos III. Fondo de Investigación Sanitaria. Ayudas PI12/00241, PI12/00324, PI15/00303 y RETICS RD12/0013/0002 Junta de Extremadura y Fondos FEDER. Ayuda GR15026peerReviewe

Detoxifying enzymes at the cross-roads of inflammation, oxidative stress, and drug hypersensitivity: role of glutathione transferase P1-1 and aldose reductase

9 p.-2 figPhase I and II enzymes are involved in the metabolism of endogenous reactive compounds as well as xenobiotics, including toxicants and drugs. Genotyping studies have established several drug metabolizing enzymes as markers for risk of drug hypersensitivity. However, other candidates are emerging that are involved in drug metabolism but also in the generation of danger or costimulatory signals. Enzymes such as aldo-keto reductases (AKR) and glutathione transferases (GST) metabolize prostaglandins and reactive aldehydes with proinflammatory activity, as well as drugs and/or their reactive metabolites. In addition, their metabolic activity can have important consequences for the cellular redox status, and impacts the inflammatory response as well as the balance of inflammatory mediators, which can modulate epigenetic factors and cooperate or interfere with drug-adduct formation. These enzymes are, in turn, targets for covalent modification and regulation by oxidative stress, inflammatory mediators, and drugs. Therefore, they constitute a platform for a complex set of interactions involving drug metabolism, protein haptenation, modulation of the inflammatory response, and/or generation of danger signals with implications in drug hypersensitivity reactions. Moreover, increasing evidence supports their involvement in allergic processes. Here, we will focus on GSTP1-1 and aldose reductase (AKR1B1) and provide a perspective for their involvement in drug hypersensitivityThis work has been supported by grants SAF2012-36519 from MINECO and SAF-2015-68590-R from MINECO/FEDER and ISCIII RETIC RIRAAF RD12/0013/0008 to DP,and RD12/0013/0002 to J A.Peer reviewe

Toward a clinical practice guide in pharmacogenomics testing for functional polymorphisms of drug-metabolizing enzymes. Gene/drug pairs and barriers perceived in Spain

The development of clinica lpractice recommendations or guidelines for the clinical use of biomarkers is an issue of great importance withr regard to adverse drug reactions.The poten-tial of pharmacogenomicbiomarkers has been extensively investigated in recent years.However,several barriers to implementing the use of pharmacogenomics testing exist.We conducted a survey among members of the Spanish Societies of Pharmacology and Clinical Pharmacology to obtain information about the perception of such barriers and to compare the perceptions of participants about the relative importance of majorgene/drug pairs.Of 11 potential barriers,the highest importance was attributed to lack of institutional support for pharmacogenomic stesting,and to the issues related to the lack of guidelines.Of the proposed gene/drug pairs the highest importance was assigned to HLA-B/abacavir, UGT1A1/irinotecan, and CYP2D6/tamoxifen.In this perspective article,we compare the relative importance of 29 gene/drugpairs in the Spanish study with that of the same pairs in the American Society for Clinical Pharmacology and Therapeutic sstudy,and we provide suggestions and areas of focus to develop a guide for clinical practice in pharmacogenomics testingThe work in the author’s laboratory is financed by Grants PS09/00943, PS09/00469, RETICS RIRAAF RD07/0064/0016, and CIBERehd from Instituto de Salud CarlosIII,Madrid, Spain, and by Grants GR10068 from Junta de Extremadura, Spain. Financed in part with FEDER funds from the European Unio

NSAIDs-hypersensitivity often induces a blended reaction pattern involving multiple organs

Las reacciones de hipersensibilidad inducidas por medicamentos antiinflamatorios no esteroideos (AINE) están clasificadas por la Red Europea de Alergia a los Medicamentos (ENDA) como reacciones cruzadas o selectivas. La primera es el tipo más frecuente e incluye a los pacientes con síntomas exclusivamente respiratorios (AINE - enfermedad respiratoria exacerbada, ENDA) o exclusivamente cutáneos: urticaria/angioedema inducido por AINEs (NIUA); y enfermedad cutánea exacerbada por AINEs (NECD). Sin embargo, aunque no se refleja en el esquema de clasificación actual (ENDA), en la práctica clínica se observa con frecuencia una combinación de síntomas tanto cutáneos como respiratorios o incluso de otros órganos, como los síntomas del tracto gastrointestinal (reacciones mixtas o combinadas). Esta entidad no ha sido suficientemente caracterizada. Nuestro objetivo era caracterizar clínicamente las reacciones mixtas a los AINEs, comparando sus características clínicas con las del NERD y la NIUA. Evaluamos a los pacientes con síntomas que sugerían hipersensibilidad a los AINEs que acudieron a la Unidad de Alergia del Hospital Universitario Regional de Málaga (Málaga, España) entre 2008 y 2015. Se incluyeron 880 pacientes con reacción cruzada confirmada en base a la historia clínica, prueba de provocación nasal positiva con acetilsalicilato de lisina (NPT-LASA) y/o prueba de provocación de drogas positiva (DPT) con ácido acetilsalicílico (ASA), que se clasificaron como mezclados (261; 29,6%), NERD (108; 12,3%) o NIUA (511; 58,1%). Se compararon los síntomas, los medicamentos, las enfermedades subyacentes y los métodos de diagnóstico dentro de los grupos y entre ellos. Entre los pacientes mezclados, el subgrupo más común comprendía aquellos que desarrollaban urticaria/angioedema más rinitis/asma (n = 138), que tenían un mayor porcentaje de rinitis subyacente (p < 0,0001) y asma (p < 0,0001) que los pacientes de NIUA, mostrando similitudes con la NERD. Estas diferencias no se encontraron en el subgrupo de pacientes mezclados que desarrollaron síntomas respiratorios como el edema de la glotis; estos eran más similares a la NIUA. El porcentaje de NPT-LASA positivo fue similar para los grupos de mezcla (77%) y NERD (78,7%). Concluimos que las reacciones mixtas son reacciones de hipersensibilidad a los AINEs que afectan al menos a dos órganos. Además de la clásica afectación cutánea y respiratoria, en nuestra población algunos pacientes también desarrollan síntomas gastrointestinales. Dada la alta tasa de respuestas positivas al NPT-LASA en el NERD así como las reacciones mixtas, sugerimos que todos los pacientes que reporten síntomas respiratorios, independientemente de si tienen otros síntomas asociados, deben ser evaluados inicialmente usando el NPT-LASA, lo cual representa menos riesgo que el DPT.Non-steroidal anti-inflammatory drugs (NSAIDs)-induced hypersensitivity reactions are classified by the European Network on Drug Allergy (ENDA) as either cross-reactive or selective. The former is the most frequent type and includes patients with exclusively respiratory symptoms (NSAIDs-exacerbated respiratory disease, NERD) or exclusively cutaneous symptoms: NSAIDs-induced urticaria/angioedema (NIUA); and NSAIDs-exacerbated cutaneous disease (NECD). However, although not reflected in the current classification scheme (ENDA), in clinical practice a combination of both skin and respiratory symptoms or even other organs such as gastrointestinal tract symptoms (mixed or blended reactions) is frequently observed. This entity has not been sufficiently characterised. Our aim was to clinically characterize blended reactions to NSAIDs, comparing their clinical features with NERD and NIUA. We evaluated patients with symptoms suggestive of hypersensitivity to NSAIDs who attended the Allergy Unit of the Regional University Hospital of Malaga (Malaga, Spain) between 2008 and 2015. We included 880 patients confirmed as cross-reactive based on clinical history, positive nasal provocation test with lysine acetylsalicylate (NPT-LASA), and/or positive drug provocation test (DPT) with acetylsalicylic acid (ASA), who were classified as blended (261; 29.6%), NERD (108; 12.3%) or NIUA (511; 58.1%). We compared symptoms, drugs, underlying diseases and diagnostic methods within and between groups. Among blended patients the most common sub-group comprised those developing urticaria/angioedema plus rhinitis/asthma (n = 138), who had a higher percentage of underlying rhinitis (p < 0.0001) and asthma (p < 0.0001) than NIUA patients, showing similarities to NERD. These differences were not found in the sub-group of blended patients who developed such respiratory symptoms as glottis oedema; these were more similar to NIUA. The percentage of positive NPT-LASA was similar for blended (77%) and NERD groups (78.7%). We conclude that blended reactions are hypersensitivity reactions to NSAIDs affecting at least two organs. In addition to classical skin and respiratory involvement, in our population a number of patients also develop gastrointestinal symptoms. Given the high rate of positive responses to NPT-LASA in NERD as well as blended reactions, we suggest that all patients reporting respiratory symptoms, regardless of whether they have other associated symptoms, should be initially evaluated using NPT-LASA, which poses less risk than DPT.• Gobierno de Andalucía. Ayuda PI-0463-2013 • Instituto de Salud Carlos III y Fondo Europeo Regional de Desarrollo. Ayuda RETIC ARADyAL RD16/0006/0001 y PI17/1253 • Sociedad Española de Alergología. Fondo de Investigación de la Fundación de la SEAIC 2016 • Instituto de Salud Carlos III, Ministerio de Economía y Competitividad y Fondo Europeo Social. Contrato de investigación Juan Rodes JR15/00036, para Inmaculada Doña Díaz. Contrato Río Hortega CM16/0067, para Gádor Bogas Herrera. Programa Miguel Servet CP14/00034, para José Antonio Cornejo García. Programa Sara Borrell CD14/00242, para James Richard Perkins.peerReviewe

Asthma and rhinitis induced by selective immediate reactions to paracetamol and non-steroidal anti-inflammatory drugs in aspirin tolerant subjects

En sujetos con anti-inflamatorios no esteroideos (AINES) se agravan las enfermedades respiratorias (ERNE) y los síntomas son desencadenados por el ácido acetilsalicílico (AAS) y otros potentes inhibidores COX-1 y, en algunos casos, por la debilidad de la COX-1 o los inhibidores selectivos de la COX-2. El mecanismo está relacionado con la prostaglandina vía inhibición y la liberación de leucotrienos. Los sujetos que reaccionan a un solo AINES y toleran otros se consideran respondedores selectivos, y a menudo presentan urticaria y/o angioedema y anafilaxia (SNIUAA). Un mecanismo inmunológico está implicado en estas reacciones. Sin embargo, la evidencia anecdótica sugiere que los respondedores selectivos que presentan síntomas de las vías respiratorias también pueden existir en los síntomas respiratorios. Nuestro objetivo fue determinar si los sujetos pueden desarrollar respuestas selectivas a los AINES/paracetamol que se manifiestan como vías respiratorias superiores/inferiores de los síntomas respiratorios. Para ello, estudiamos informes de pacientes con rinitis y/o asma inducida por el paracetamol o un único NSAID que tolera la ASA. Una evaluación alergológica plus reto, controlados con ASA, se llevó a cabo. Si la tolerancia ASA se encuentra, se procede a una provocación oral con el fármaco responsable. La aparición de los síntomas fue supervisada por un cuestionario clínico, midiendo el FEV1 y/o las vías respiratorias nasales y los cambios de volumen pre y post-desafío. De un total de 21 casos iniciales, hemos confirmado la aparición de problemas nasales y/o manifestaciones bronquiales en diez, caracterizados por una disminución significativa en el VEF1% y/o una disminución en el volumen de la cavidad nasal tras la administración del fármaco. Todos los casos tolerados cuentan con ASA. Esto demuestra que los sujetos con tolerante ASA presentan manifestaciones sistémicas de rinitis y/o asma inducida por el paracetamol o un único NSAID sin piel. Se requiere más investigación para saber si estos pacientes representan un nuevo fenotipo clínico para ser incluido dentro de la actual clasificación de las reacciones de hipersensibilidad a AINES.In subjects with non-steroidal anti-inflammatory drugs (NSAIDs)- exacerbated respiratory disease (NERD) symptoms are triggered by acetyl salicylic acid (ASA) and other strong COX-1 inhibitors, and in some cases by weak COX-1 or by selective COX-2 inhibitors. The mechanism involved is related to prostaglandin pathway inhibition and leukotriene release. Subjects who react to a single NSAID and tolerate others are considered selective responders, and often present urticaria and/or angioedema and anaphylaxis (SNIUAA). An immunological mechanism is implicated in these reactions. However, anecdotal evidence suggests that selective responders who present respiratory airway symptoms may also exist. Our objective was to determine if subjects might develop selective responses to NSAIDs/paracetamol that manifest as upper/lower airways respiratory symptoms. For this purpose, we studied patients reporting asthma and/or rhinitis induced by paracetamol or a single NSAID that tolerated ASA. An allergological evaluation plus controlled challenge with ASA was carried out. If ASA tolerance was found, we proceeded with an oral challenge with the culprit drug. The appearance of symptoms was monitored by a clinical questionnaire and by measuring FEV1 and/or nasal airways volume changes pre and post challenge. From a total of 21 initial cases, we confirmed the appearance of nasal and/or bronchial manifestations in ten, characterized by a significant decrease in FEV1% and/or a decrease in nasal volume cavity after drug administration. All cases tolerated ASA. This shows that ASA tolerant subjects with asthma and/or rhinitis induced by paracetamol or a single NSAID without skin/systemic manifestations exist. Whether these patients represent a new clinical phenotype to be included within the current classification of hypersensitivity reactions to NSAIDs requires further investigation.Trabajo patrocinado por: Programa Miguel Servet. Ref CP14/00034, para José Antonio Cornejo García Ministerio de Economía y Competitividad y Instituto Nacional de Salud Carlos III y Fondos FEDER. Programa Sara Borrell. Ref. CD14/00242, para James R. Perkins Ministerio de Economía y Competitividad e Instituto Nacional de Salud Carlos III y Fondos FEDER. Becas FISPI12/02247, FISPI13/02598, FISPI15/00726 y FIS PI15/00303 Servicio Público de Salud de Andalucía. Becas PI-0279-2012 y PI-0463- 2013 Junta de Extremadura y Fondos FEDER. Beca GR15026peerReviewe

GC gene polymorphism and unbound serum retinol-binding protein 4 are related to the risk of insulin resistance in patients with chronic hepatitis c: A prospective cross-sectional study

Insulin resistance (IR) is found in chronic hepatitis C (CHC) more frequently than in other chronic liver diseases. Prospective cross-sectional study to evaluate a wide multitest panel to identify factors related with IR in CHC and their possible interactions. In 76 patients with CHC we performed a series of routine laboratory analysis as well as specifically designed serum biochemical tests [retinol, retinol-binding protein 4 (RBP4), 25-OH vitamin D, Vitamin E, lipopolysaccharide-binding protein (LBP), interleukin-6 (IL-6), and cystatin C]. The single nucleotide polymorphisms rs7041 and rs4588 GC-DBP (group-specific component-Vitamin D-binding protein), rs738409 PNPLA3 (patatin-like phospholipase domain containing 3), and rs12979860 IL28B (interleukin-28 B) genes were determined. Insulin sensitivity was established with the HOMA-IR and IR was diagnosed when HOMA-IR>3. Fibrosis staging was assessed with liver biopsy or transient elastography. After backward logistic regression analysis, independent variables associated with IR were Gc1s/Gc1s DBP phenotype, that results from the homozygous carriage of the rs7041G/rs4588Chaplotype (P¼0.033); low retinol/RBP4 ratio, reflecting a greater rate of unboundRBP4 (P¼0.005); older age (P¼0.01); high serum tryglicerides (P¼0.026); and advanced (F3–F4) fibrosis stage. The AUROC provided by the multivariate model was 0.950 (95% CI¼0.906–0.993). In addition to previously known ones, the Gc1s/Gc1s phenotype variant of DBP and the unbound fraction of plasma RBP4 may be considered as factors related with the incidence, and possibly the risk, of IR in CHC patients.• Instituto de Salud Carlos III, Fondo de Investigación Sanitari: Ayudas PI12/00241 y PI12/00324 • Junta de Extremadura: Ayuda GR15026 • Fondos FEDERpeerReviewe

A nonsynonymous FCER1B SNP is associated with risk of developing allergic rhinitis and with IgE levels

Allergic rhinitis is associated with elevated serum IgE levels. IgE response is mediated by the highaffinity IgE receptor (FcεRI), which is polymorphic. Studies analyzing the association between allergic rhinitis and FcεRI variants have been conducted with controversial results. The objective of this study is to analyze, in 1,041 individuals, the putative clinical association of allergic rhinitis with common polymorphisms in FcεRI subunits genes. These SNPs included FECR1A rs2494262, rs2427837 and rs2251746; FECR1B rs1441586, rs569108 and rs512555; FCER1G rs11587213, rs2070901 and rs11421. Statistically significant differences were observed for the FCER1B rs569108 and rs512555 polymorphisms frequencies when comparing patients with allergic rhinitis without asthma and controls. The OR (95% CI) value for the 237Gly allele (rs569108) is equal to 0.26 (0.08–0.86, P = 0.017) and for the G allele (rs512555) it is equal to 0.27 (0.08–0.88, P = 0.020). These two SNPs are linked (D’ = 1.0, LOD = 56.05). Also observed was a statistically significant trend towards lower IgE values among allergic rhinitis patients with variant alleles for both SNPs. In conclusion, in patients with allergic rhinitis without asthma, the FCER1B rs569108 and rs512555 polymorphisms are associated with increased risk of developing allergic rhinitis and with lower IgE levels.Trabajo financiado por: Instituto de Salud Carlos III. Fondo de Investigación Sanitaria. Becas PI12/00241, PI12/00324 y RETICS RD12/0013/0002 Junta de Extremadura y Fondos FEDER. Ayuda GR15026peerReviewe

Heme oxygenase 1 and 2 common genetic variants and risk for essential tremor

Varios informes sugirieren que una función hemo oxigenasa 1 y 2 de los genes HMOX HMOX1 y 2 modifican el riesgo de desarrollar la enfermedad de Parkinson (EP). Porque el temblor esencial (ET) y PD comparten fenotipo y, probablemente, unos factores etiológicos semejantes, analizamos si tales genes están relacionados con el riesgo de desarrollar ET. Se analizó la distribución de las frecuencias genotípicas y alélicas de los HMOX1 rs2071746, HMOX1 rs2071747, HMOX2 rs2270363 y rs1051308 HMOX2 polimorfismos de nucleótido único, así como la presencia de variaciones de número de copias de estos genes en 202 sujetos con ET familiar y 747 controles sanos. Las frecuencias alélicas de rs2071746T y R1051308G ET fueron significativamente menores en los pacientes que en los controles. Ninguno de los polimorfismos estudiados influyeron en el comienzo de la enfermedad. El presente estudio sugiere una débil asociación entre HMOX1 rs2071746 y rs1051308 HMOX2 polimorfismo y el riesgo de desarrollar ET en la población española.Several reports suggested a role of heme oxygenase genes 1 and 2 (HMOX1 and HMOX2) in modifying the risk to develop Parkinson disease (PD). Because essential tremor (ET) and PD share phenotypical and, probably, etiologic factors of the similarities, we analyzed whether such genes are related with the risk to develop ET. We analyzed the distribution of allelic and genotype frequencies of the HMOX1 rs2071746, HMOX1 rs2071747, HMOX2 rs2270363, and HMOX2 rs1051308 single nucleotide polymorphisms, as well as the presence of copy number variations of these genes in 202 subjects with familial ET and 747 healthy controls. Allelic frequencies of rs2071746T and rs1051308G were significantly lower in ET patients than in controls. None of the studied polymorphisms influenced the disease onset. The present study suggests a weak association between HMOX1 rs2071746 and HMOX2 rs1051308 polymorphisms and the risk to develop ET in the Spanish population.T• Instituto de Salud Carlos III, Fondo de Investigación Sanitaria: Ayudas PI12/00241, PI12/00324 y RETICS RD12/0013/0002 • Junta de Extremadura: Ayuda GR10068 • Ministerio de Ciencia e Innovación: Ayudas SAF2006-10126 (2006–2009) y SAF2010-22329-C02-01 (2011–2013) • Parcialmente financiado Fondos FEDER – Fondo Europeo de Desarrollo RegionalpeerReviewe

Association between vitamin D receptor rs731236 (Taq1) polymorphism and risk for restless legs syndrome in the Spanish caucasian population

Varios trabajos recientes sugieren un posible papel de la deficiencia de vitamina D en la etiología o el síndrome de las piernas inquietas (RLS). Hemos analizado la posible relación de 2 polimorfismos de un solo nucleótido (SNP) en el receptor de la vitamina D3 (GEN VDR) con el riesgo de SPI. Hemos estudiado la variante alélica genotipo y frecuencias de VDR rs2228570 y rs731236 VDR SNPs en 205 RLS pacientes y 445 controles sanos mediante un ensayo TaqMan. Las frecuencias de los rs731236AAgenotype y la variante alélica rs731236un SPI fue significativamente inferior en los pacientes que en los controles (P<0,005 y 0,01, respectivamente). El síndrome de las piernas inquietas pacientes portadoras de la variante alélica rs731236G había una edad temprana en el inicio, y los portadores del genotipo GG731236rs tuvieron mayor severidad de RLS, aunque estos datos desaparecieron después de los análisis multivariados. Ninguno de los SNPs estudiados estaba relacionada con la positividad de la historia familiar de SPI. Estos resultados sugieren una modesta, pero significativa asociación entre rs731236 VDR SNP y el riesgo de síndrome de piernas inquietas.Several recent works suggest a possible role of vitamin D deficiency in the etiology or restless legs syndrome (RLS). We analyzed the possible relationship of 2 common single nucleotide polymorphisms (SNPs) in the vitamin D3 receptor (VDR) gene with the risk for RLS. We studied the genotype and allelic variant frequencies of VDR rs2228570 and VDR rs731236 SNPs in 205 RLS patients and 445 healthy controls using a TaqMan essay. The frequencies of the rs731236AAgenotype and the allelic variant rs731236A were significantly lower in RLS patients than in controls (P<0.005 and<0.01, respectively). Restless legs syndrome patients carrying the allelic variant rs731236G had an earlier age at onset, and those carrying the rs731236GG genotype had higher severity of RLS, although these data disappeared after multivariate analyses. None of the SNPs studied was related with the positivity of family history of RLS. These results suggest a modest, but significant association between VDR rs731236 SNP and the risk for RLS.• Instituto de Salud Carlos III, Madrid, Fondo de Investigación Sanitaria: Ayudas PI12/00241, PI12/00324, y RETICS RD12/0013/0002 • Junta de Extremadura: GR15026 y PRIS10016 • Ministerio de Ciencia e Innovación: Ayudas SAF2006-10126 (2006–2009) y SAF2010-22329-C02-01 (2011-2013) • Parciamente financiado con Fondos FEDERpeerReviewe

Heme oxygenase-1 and 2 common genetic variants and risk for restless legs syndrome

Varios neurotransmisores, neuropatológicos, neuroimagen, y los datos experimentales, sugieren que la deficiencia de hierro juega un papel importante en la fisiopatología del síndrome de piernas inquietas (RLS). HMOX (Hemeoxygenases) es un importante mecanismo de defensa contra el estrés oxidativo, principalmente a través de la degradación del hemo a biliverdin, libre de hierro, y monóxido de carbono. Hemos analizado si los genes HMOX1 y HMOX2 están relacionados con el riesgo de desarrollar el síndrome de piernas inquietas. Se analizó la distribución de genotipos y las frecuencias alélicas de los HMOX1 rs2071746, HMOX1 rs2071747, HMOX2 rs2270363 y rs1051308 HMOX2 SNPs, así como la presencia de variaciones de número de copia (CNVs) de estos genes en 205 sujetos RLS y 445 controles sanos. Las frecuencias de rs2071746 genotipo TT y R2071746T variante alélica fueron significativamente inferiores en los pacientes de SPI que en controles, aunque los otros 3 SNPs estudiados RLS no difirió entre pacientes y controles. Ninguno de los polimorfismos estudiados influyeron en el inicio de la enfermedad, la gravedad de la RLS, historia familiar de SPI, la ferritina sérica, o respuesta a agonistas dopaminérgicos, clonazepam o GABAergic drogas. El presente estudio sugiere una débil asociación entre el polimorfismo rs2071746 HMOX1 y el riesgo de desarrollar el SPI en la población española.Several neurochemical, neuropathological, neuroimaging, and experimental data, suggest that iron deficiency plays an important role in the pathophysiology of restless legs syndrome (RLS). Hemeoxygenases (HMOX) are an important defensive mechanism against oxidative stress, mainly through the degradation of heme to biliverdin, free iron, and carbon monoxide. We analyzed whether HMOX1 and HMOX2 genes are related with the risk to develop RLS. We analyzed the distribution of genotypes and allelic frequencies of the HMOX1 rs2071746, HMOX1 rs2071747, HMOX2 rs2270363, and HMOX2 rs1051308 SNPs, as well as the presence of Copy number variations (CNVs) of these genes in 205 subjects RLS and 445 healthy controls. The frequencies of rs2071746TT genotype and rs2071746T allelic variant were significantly lower in RLS patients than that in controls, although the other 3 studied SNPs did not differ between RLS patients and controls. None of the studied polymorphisms influenced the disease onset, severity of RLS, family history of RLS, serum ferritin levels, or response to dopaminergic agonist, clonazepam or GABAergic drugs. The present study suggests a weak association between HMOX1 rs2071746 polymorphism and the risk to develop RLS in the Spanish population.• Instituto de Salud Carlos III, Fondo de Investigación Sanitaria: Ayudas PI12/00241, PI12/00324 y RETICS RD12/0013/0002 • Junta de Extremadura: Ayuda GR10068 GR10068 y PRIS10016 (Fundesalud,Mérida, Spain) • Ministerio de Ciencia e Innovación: Ayudas SAF2006-10126 (2006–2009) y SAF2010-22329-C02-01 (2011–2013) • Parcialmente financiado Fondos FEDER – Fondo Europeo de Desarrollo RegionalpeerReviewe