Identification of a major susceptibility locus for restless legs syndrome on chromosome 12q

Clinical and genetic description of a family with a high prevalence of autosomal dominant restless legs syndrome

OBJECTIVE

To conduct clinical and molecular genetic analyses of the members of an extended family in Central Indiana with a high prevalence of restless legs syndrome (RLS).

PARTICIPANTS AND METHODS

From February 1, 2006, through August 31, 2008, we collected data from members of this family, which is of English descent. Genealogical methods were used to expand the family tree, and family members were screened with an RLS questionnaire. Telephone interviews and personal examinations were performed at Mayo Clinic and during a field trip to Central Indiana. Blood samples were collected for molecular genetic analysis. A follow-up telephone interview was conducted 1 year later.

RESULTS

The family tree spans 7 generations with 88 living members, 30 of whom meet the criteria for diagnosis of RLS established by the International Restless Legs Syndrome Study Group. Three affected family members also have Parkinson disease or essential tremor. The mode of RLS inheritance is compatible with an autosomal dominant pattern. The affected family members do not exhibit linkage to the 5 known RLS loci or mutations in the RLS susceptibility genes MEIS1 and BTBD9.

CONCLUSION

Of 88 members of this single extended family in Central Indiana, 30 were diagnosed as having RLS. Because our analysis shows that the disease is not linked to any of the known RLS loci or risk-associated genes, we postulate that members of this family may carry a gene mutation in a novel genetic locus.

Clinical and genetic description of a family with a high prevalence of autosomal dominant restless legs syndrome

OBJECTIVE

To conduct clinical and molecular genetic analyses of the members of an extended family in Central Indiana with a high prevalence of restless legs syndrome (RLS).

PARTICIPANTS AND METHODS

From February 1, 2006, through August 31, 2008, we collected data from members of this family, which is of English descent. Genealogical methods were used to expand the family tree, and family members were screened with an RLS questionnaire. Telephone interviews and personal examinations were performed at Mayo Clinic and during a field trip to Central Indiana. Blood samples were collected for molecular genetic analysis. A follow-up telephone interview was conducted 1 year later.

RESULTS

The family tree spans 7 generations with 88 living members, 30 of whom meet the criteria for diagnosis of RLS established by the International Restless Legs Syndrome Study Group. Three affected family members also have Parkinson disease or essential tremor. The mode of RLS inheritance is compatible with an autosomal dominant pattern. The affected family members do not exhibit linkage to the 5 known RLS loci or mutations in the RLS susceptibility genes MEIS1 and BTBD9.

CONCLUSION

Of 88 members of this single extended family in Central Indiana, 30 were diagnosed as having RLS. Because our analysis shows that the disease is not linked to any of the known RLS loci or risk-associated genes, we postulate that members of this family may carry a gene mutation in a novel genetic locus.

Restless legs syndrome: differential diagnosis and management with rotigotine

RLS is a common sleep disorder with distinctive clinical features. The prevalence of RLS in Caucasians and North Americans ranges from 5% to 10%. However, only some of these subjects (almost the 3% of the general population) report being affected by a frequent and severe form of the sleep disorder. RLS is diagnosed clinically by means of four internationally recognized criteria that summarize the main characteristics of the sleep disorder. Besides the essential criteria, supportive and associated features of RLS have been established by experts in order to help physicians treat patients with doubtful symptoms. Several clinical conditions may mimic this sleep disorder. In order to increase the sensibility and specificity of RLS diagnosis, doctors should perform a meticulous patient history and then an accurate physical and neurological examination. Dopamine agonists are recognized as the preferred first-line treatment for RLS. Rotigotine is a non-ergoline dopamine agonist with selectivity for D1, D2 and D3 receptors. The drug is administered via transdermal patches which release rotigotine for 24 hours. Four clinical trials demonstrated that this compound is able to improve RLS symptomatology with few and moderate adverse events. Head to head trials are required to compare the efficacy and tolerability of rotigotine with other dopamine agonists administered via oral intake. Rotigotine has been approved by the FDA and EMEA for Parkinson's disease. For the treatment of moderate to severe idiopathic RLS, rotigotine has been recommended for approval by the EMEA and is under review by the FDA.

Restless legs syndrome: a unique case and essentials of diagnosis and treatment

Restless legs syndrome (RLS) is a common, poorly understood movement disorder that can cause significant sleep disruption. RLS is characterized by uncomfortable sensations deep in the legs, relieved only by voluntary movement. Differential diagnosis includes peripheral neuropathy, leg cramps, and akathesia. Although RLS is familial in 50% of cases, secondary etiologies can be medically important, such as iron deficiency anemia and renal failure. We report a rare case of RLS associated with hyperparathyroidism. To our knowledge, only 1 other case of hyperparathyroid-related RLS has been described.

Restless legs syndrome: pathophysiology, diagnosis and treatment

Restless legs syndrome (RLS) is clinically defined by the presence of (i) an urge to move the legs with or without an actual paraesthesia; (ii) a worsening of symptoms with inactivity; (iii) improvement with activity; and (iv) a worsening of symptoms in the evening and at night. Patients may use a variety of semantic phrases to describe their symptoms but all must have an urge to move. Most people with RLS also have periodic limb movements during sleep, although this is not part of the clinical diagnostic criteria. RLS is very common. About 10% of all Caucasian populations have RLS, although it may be mild in the majority of cases. Women generally outnumber men by about 2:1. As a general rule, RLS severity worsens through the first seven to eight decades of life, but may actually lessen in old age. The aetiology of RLS is only partly understood. There is a strong genetic component, and several genetic linkages and three causative genes have been identified worldwide. Several medical conditions, including renal failure, systemic iron deficiency and pregnancy, and possibly neuropathy, essential tremor and some genetic ataxias, are also associated with high rates of RLS. In all cases to date, the actual CNS pathology of RLS demonstrates reduced iron stores, in a pattern that suggests that the homeostatic control of iron is altered, not just that there is not enough iron entering the brain. The relationship between reduced CNS iron levels and the clinical phenotype or treatment response to dopaminergics is not known but generates promising speculation. Treatment of RLS is usually rewarding. Most patients respond robustly to dopamine receptor agonists. Over time, response may lessen, or the patients may develop 'augmentation', whereby they have a worsening of symptoms, usually in the form of an earlier onset. Other treatment options include gabapentin, or similar antiepileptic drugs, and opioids. High-dose intravenous iron is a promising but still experimental approach.

Genetics of restless legs syndrome

Restless legs syndrome (RLS) is a highly familial trait with heritability estimates of about 50%. It is a polygenetic disorder in which a number of variants contribute to the phenotype. Linkage studies in families with RLS revealed several loci but have not yet led to the identification of disease-causing sequence variants. Phenocopies, nonpenetrance, and possible intrafamilial heterogeneity make it difficult to define the exact candidate region. Genome-wide association studies identified variants within intronic or intergenic regions of MEIS1, BTBD9, and MAP2K5/LBOXCOR1. Carriers of one risk allele had a 50% increased risk of developing RLS. MEIS1 and LBXCOR1 are developmental factors and raise new pathophysiologic questions for RLS. These variants have weak and moderate effects and increase the risk of developing RLS. It is still possible that strong effects explain the occurrence of RLS in families. Therefore, linkage and association studies should be used congruently to dissect the complete genetic architecture of RLS.

Restless legs syndrome in type 2 diabetes: implications to diabetes educators

PURPOSE

The purpose of this study was to provide a background of restless legs syndrome (RLS), present the prevalence and demographic findings of a descriptive study of type 2 diabetes with RLS, and provide implications to diabetes educators on the management and education of RLS.

METHODS

Participants with type 2 diabetes who met the diagnostic criteria for RLS based on the International RLS Study Group Criteria were recruited from the PENN Rodebaugh Diabetes Center from July 2005 through September 2006. Participants who met inclusion and exclusion criteria were mailed a survey to collect data.

RESULTS

Of 121 patients with type 2 diabetes, 54 (45%) of the screened sample met the 4 diagnostic criteria for RLS. Of those who met the inclusion and exclusion criteria of the primary study, 18 patients with type 2 diabetes with RLS participated in this study. Along with diabetes, the participants had a variety of comorbid health conditions including hypertension, neuropathies, rheumatoid arthritis, renal failure, and irritable bowel syndrome. Only one third of the participants were being treated for RLS. Thirty-nine percent of the participants with type 2 diabetes were using insulin to manage their diabetes with other oral agents.

CONCLUSIONS

RLS is a sleep disorder that may affect the management of type 2 diabetes. Diabetes educators must know that sleep disorders can affect long-term health outcomes, and RLS is frequently seen in this cohort of patients.

[Restless-legs syndrome]

Restless-legs syndrome (RLS) is a sensorimotor disorder, characterized by an irresistible urge to move the legs usually accompanied or caused by uncomfortable and unpleasant sensations. It begins or worsens during periods of rest or inactivity, is partially or totally relieved by movements and is exacerbated or occurs at night and in the evening. RLS sufferers represent 2 to 3% of the general population in Western countries. Supportive criteria include a family history, the presence of periodic-leg movements (PLM) when awake or asleep and a positive response to dopaminergic treatment. The RLS phenotypes include an early onset form, usually idiopathic with a familial history and a late onset form, usually secondary to peripheral neuropathy. Recently, an atypical RLS phenotype without PLM and l-DOPA resistant has been characterized. RLS can occur in childhood and should be distinguished from attention deficit/hyperactivity disorder, growing pains and sleep complaints in childhood. RLS should be included in the diagnosis of all patients consulting for sleep complaints or discomfort in the lower limbs. It should be differentiated from akathisia, that is, an urge to move the whole body without uncomfortable sensations. Polysomnographic studies and the suggested immobilization test can detect PLM. Furthermore, an l-DOPA challenge has recently been validated to support the diagnosis of RLS. RLS may cause severe-sleep disturbances, poor quality of life, depressive and anxious symptoms and may be a risk factor for cardiovascular disease. In most cases, RLS is idiopathic. It may also be secondary to iron deficiency, end-stage renal disease, pregnancy, peripheral neuropathy and drugs, such as antipsychotics and antidepressants. The small-fiber neuropathy can mimic RLS or even trigger it. RLS is associated with many neurological and sleep disorders including Parkinson's disease, but does not predispose to these diseases. The pathophysiology of RLS includes an altered brain-iron metabolism, a dopaminergic dysfunction, a probable role of pain control systems and a genetic susceptibility with nine loci and three polymorphisms in genes serving developmental functions. RLS treatment begins with the elimination of triggering factors and iron supplementation when deficient. Mild or intermittent RLS is usually treated with low doses of l-DOPA or codeine; the first-line treatment for moderate to severe RLS is dopaminergic agonists (pramipexole, ropinirole, rotigotine). In severe, refractory or neuropathy-associated RLS, antiepileptic (gabapentin, pregabalin) or opioid (oxycodone, tramadol) drugs can be used.

Internal medicine: guidance to the diagnosis and management of restless legs syndrome

Restless legs syndrome (RLS) is a chronic neurologic disorder, with a prevalence rate in the general population of 5% to 10%. The diagnosis of RLS is straightforward; it is based on symptom history alone and uses the four essential diagnostic criteria for RLS. Owing to the heterogeneity of the disorder, the sensory and motor symptoms of RLS are often attributed to other disorders, and many patients remain undiagnosed and untreated. The symptoms of RLS are thought to result from a central dopaminergic dysfunction. Dopamine agonists are considered first-line treatment for moderate-to-severe primary RLS, although other nondopaminergic therapies are sometimes used to ease the symptoms of RLS. This article will guide primary care and internal medicine specialists through the diagnosis and management options of primary RLS.

Genetic association studies of neurotensin gene and restless legs syndrome in French Canadians

BACKGROUND AND PURPOSE

The neurotensin gene (NTS), a known dopamine modulator, is located within the candidate region for the first genetic locus of restless legs syndrome (RLS1) on chromosome 12q. Though no causative mutation was found in selected patients in a previous mutation analysis, the involvement of NTS in RLS cannot be completely excluded as a potential positional and functional candidate gene. The purpose of the current study is to further explore the NTS gene for potential functional variant(s) in its entire genomic and potential regulatory regions and their possible association with RLS symptoms.

METHODS AND SUBJECTS

We resequenced the coding regions and sequenced all the intronic and potential regulatory regions of the NTS gene in additional patients and controls. We carried out full scale gene-based case-control and family-based genetic association studies using the sequence variants detected during mutational analysis.

RESULTS

No coding or variants in regulatory and intronic regions compatible with a deleterious mutation were detected. Seven polymorphisms with elevated allele frequencies in the Caucasian population did not show association with RLS in two independent case-control groups and 110 RLS families.

CONCLUSION

The NTS gene on chromosome 12q is most unlikely to play a direct role in RLS etiology.

Genetics of restless legs syndrome (RLS): State-of-the-art and future directions

Several studies demonstrated that 60% of restless legs syndrome (RLS) patients have a positive family history and it has been suggested that RLS is a highly hereditary trait. To date, several loci have been mapped but no gene has been identified yet. Phenocopies and possible nonpenetrants made it difficult to detect a common segregating haplotype within the families. Defining the exact candidate region is hampered by possible intrafamilial, allelic, and nonallelic heterogeneity. One important prerequisite for future successful genetic studies in RLS is the availability of large and thoroughly phenotyped patients and family samples for linkage as well as association studies.

Suggestive evidence for linkage for restless legs syndrome on chromosome 19p13

Five loci for restless legs syndrome (RLS) on chromosomes 12q, 14q, 9p, 2q, and 20p (RLS1-RLS5) have been mapped in RLS families, with a recessive in the first and autosomal-dominant mode of inheritance in the latter cases. Investigations of further RLS families showed evidence for genetic locus heterogeneity. We have conducted a genome-wide linkage analysis in a large RLS family of Italian origin with 12 affected members in 3 generations using 5,861 single nucleotide polymorphisms (SNP, 6K Illumina). Linkage analysis was performed under an autosomal-dominant model with a complete penetrance, an allele frequency of 0.003 and a phenocopy rate of 0.005. The genome-wide scan resulted in suggestive evidence for linkage on chromosome 19p with maximum multipoint logarithm of the odds score of 2.61 between markers rs754292 and rs273265. The locus was replicated in a family-based association study in a set of 159 trios of European origin. This study provides evidence for a further RLS locus, thus supporting the picture of RLS as a genetically heterogenous complex trait.

Possible association between G-protein β3 subunit C825T polymorphism and antipsychotic-induced restless legs syndrome in schizophrenia

OBJECTIVE

The incidence of restless legs syndrome (RLS) is presumed to be higher among people with schizophrenia who take antipsychotic medication, most of which blocks the dopamine D2 receptor. The purpose of this study was to determine whether the G-protein β3 subunit (GNB3) C825T polymorphism is associated with antipsychotic-induced RLS in schizophrenia.

METHODS

We examined 178 Korean patients with schizophrenia. All of the subjects were evaluated using the diagnostic criteria of the International Restless Legs Syndrome Study Group and the International Restless Legs Scale. Genotyping was performed for the C825T polymorphism in the GNB3 gene.

RESULTS

The genotype distribution did not differ significantly between antipsychotic-induced RLS patients and patients who had no-RLS symptoms (χ 2 = 4.30, p = 0.116). The genotypes of the C825T single-nucleotide polymorphism (SNP) were classified into two groups: C+ (CC and CT genotypes) and C- (TT genotype). The presence of the C allele (C+) was associated with an increased likelihood of RLS (χ 2 = 4.14, p = 0.042; odds ratio = 2.56, 95% confidence interval = 1.02-6.47).

CONCLUSIONS

These results suggest that the GNB3 C825T SNP is associated with RLS in schizophrenia. However, confirming this association requires future larger scale studies in which the effects of medication are strictly controlled.

Restless Legs Syndrome

Restless legs syndrome is a symptomatic urge to move the legs, usually accompanied or caused by uncomfortable/ unpleasant sensations deep within the legs that begin or are worsened during periods of rest or inactivity in the evening or night and are partially or totally relieved by movement. It can occur intermittently or daily. Nonpharmacologic treatments include moderate exercise; good sleep hygiene; elimination of alcohol, caffeine, and nicotine; and hot baths, massage, and stretching. Activities promoting mental alertness may improve symptoms. Moderate exercise and use of nasal continuous positive airway pressure are the only nonpharmacologic treatments with proven benefit. For intermittent restless legs syndrome, carbidopa/levodopa and nonpharmacologic therapy are recommended as primary treatments. For daily restless legs syndrome, dopamine agonists, particularly ropinirole and pramipexole, are suggested as the drugs of choice. Carbidopa/levodopa could be considered for daily restless legs syndrome, but augmentation is a significant drawback to its use. Carbamazepine and gabapentin have limited data to support their use.

Restless legs syndrome: a common disorder in patients with rheumatologic conditions

OBJECTIVES

To review the symptoms, differential diagnosis, and treatment of the restless legs syndrome (RLS), and its relevance within rheumatologic practice.

METHODS

Review of the scientific literature on RLS to summarize symptom presentation, burden, diagnosis, treatment, and association with rheumatologic conditions.

RESULTS

RLS is a sensorimotor neurological disorder characterized by an irresistible urge to move the legs, usually accompanied or caused by unpleasant sensations within the legs. These sensations are sometimes described as achy or painful. They may cause sleep disruption and impair quality of life. RLS may be primary, of unknown etiology, with a likely genetic basis, or secondary, provoked by other conditions. Secondary RLS often improves when the underlying condition is treated or resolves. Since RLS is common in rheumatologic disorders such as rheumatoid arthritis or Sjögren's syndrome, rheumatologists need to be familiar with the condition. Primary care physicians may misattribute RLS symptoms to other conditions and refer patients to specialists for treatment. Since RLS symptoms can be similar to, and mistaken for, symptoms in rheumatologic diseases, patients may be referred to rheumatologists. Therefore, it is important that rheumatologists be able to recognize, differentiate, diagnose, and treat RLS.

CONCLUSIONS

The clinical diagnosis of RLS is based on 4 essential diagnostic criteria related to the urge to move that characterizes this disorder. Beyond good sleep hygiene and behavioral measures, dopaminergic agents are first-line treatments for primary RLS. Anticonvulsants, opioids, and sedative/hypnotics may also have a role in management.

Molecular genetic studies of DMT1 on 12q in French-Canadian restless legs syndrome patients and families

Converging evidence from clinical observations, brain imaging and pathological findings strongly indicate impaired brain iron regulation in restless legs syndrome (RLS). Animal models with mutation in (DMT1) divalent metal transporter 1 gene, an important brain iron transporter, demonstrate a similar iron deficiency profile as found in RLS brain. The human DMT1 gene, mapped to chromosome 12q near the RLS1 locus, qualifies as an excellent functional and possible positional candidate for RLS. DMT1 protein levels were assessed in lymphoblastoid cell lines from RLS patients and controls. Linkage analyses were carried out with markers flanking and within the DMT1 gene. Selected patient samples from RLS families with compatible linkage to the RLS1 locus on 12q were fully sequenced in both the coding regions and the long stretches of UTR sequences. Finally, selected sequence variants were further studied in case/control and family-based association tests. A clinical association of anemia and RLS was further confirmed in this study. There was no detectable difference in DMT1 protein levels between RLS patient lymphoblastoid cell lines and normal controls. Non-parametric linkage analyses failed to identify any significant linkage signals within the DMT1 gene region. Sequencing of selected patients did not detect any sequence variant(s) compatible with DMT1 harboring RLS causative mutation(s). Further studies did not find any association between ten SNPs, spanning the whole DMT1 gene region, and RLS affection status. Finally, two DMT1 intronic SNPs showed positive association with RLS in patients with a history of anemia, when compared to RLS patients without anemia.

Age-at-onset in restless legs syndrome: a clinical and polysomnographic study

OBJECTIVE

To determine the distribution of age-at-onset in a large cohort of patients with restless legs syndrome (RLS) and to compare clinical and polysomnographic characteristics of patients with early and late age-at-onset of RLS.

METHODS

Two hundred and fifty patients with RLS were studied. Information on age-at-onset, etiology, familial history and symptoms severity of RLS was obtained. Age-at-onset density functions were determined from bootstrap methods and kernel density estimators.

RESULTS

Age-at-onset showed a significant bimodal distribution with a large peak occurring at 20 years of age and a smaller peak in the mid-40s. Early- and late-onset RLS could be separated with a cut-off at 36 years of age. Distributions of age-at-onset differed as a function of presence/absence of a familial history and etiology of RLS. Age-at-onset clearly differentiated patients with a primary RLS (early onset) from those with secondary RLS. Finally, early-onset RLS was associated with increased RLS severity with higher indices of periodic leg movements in sleep (PLMS) associated with microarousals and periodic leg movements during wakefulness (PLMW).

CONCLUSIONS

Early- and late-onset RLS could be distinguished depending on familial history and etiology of RLS. Our data suggest that different pathological processes are involved in these two groups, the early-onset group being highly genetically determined.

In restless legs syndrome, during changes in vigilance, the forced EEG shifts from alpha activity to delta or high alpha may lead to the altered states of dopamine receptor function and the symptoms

RLS cases may carry a genetic vulnerability called EEG alpha activity gate dyscontrols which appear during changes in vigilance and generally during sleep. It is triggered by forced EEG shifts either from alpha activity to delta or high alpha. Expressions of alpha activity gate dyscontrols may have a gate effect that trigger a second vulnerability-dopamine receptor specific individual sensitivity (DRSIS) and this leads to a deficiency in dopamine transmissions at diencephalospinal dopamine system (DSDS). Due to altered gene expressions in states of dopamine receptor function, DRSIS EEGs and RLS symptoms may be interpreted as follows: A. Disinhibition state is alpha activity gate dyscontrols induced inhibition of DSDS inhibitory dopamine modulations. Dopaminergic disinhibitions inhibit inhibitory interneurons of sensory and motor nuclei neurons that are involved in RLS. These sleep sensitive inhibitory interneurons possibly have GABA-ergic functions in sleep. (I) DSDS thalamic neurons' disinhibitory effects in thalamus on GABA-ergic interneurons of: (a) Intralaminar nuclei non-discriminative sensation neurons at thalamocortical premotor network leading to symptom of "a sense of urgency to move" generally referenced to legs.(b) Reticular thalamic nucleus (RTN) neurons. At polysomnography,during NREM sleep, disinhibited RTN neurons show alpha activity gate dyscontrol 1. These are recurrent subtypes of CAP in alpha band (7-12 Hz) pointing a difficulty in shifting to subtypes of CAP in low delta bands (0.25-2.5 Hz) and sleep fragmentations.(II) Supraspinal disinhibitory projections from DSDS thalamic neurons on GABA-ergic interneurons of: (a) Sensory neurons at posterior horns of spinal cord leading to dysesthesias, generally referenced to legs.(b) Medullary-reticulospinal neurons and by way of independent spinal rhythm generators on motoneurons leading to periodic limb movements in sleep.B. Activation state is an increase in symptoms. Sensory intralaminar and motor pontin nuclei neurons are in fact excitatory but are disinhibited in RLS. Due to altered gene expression, these neurons begin to perceive 'disinhibition' as reduced inhibition. Their glutamate receptors may activate deficient dopamine transmissions on RTN leading to alpha activity gate dyscontrol 2. This implies a failure in preventing shifts to frequent subtypes of CAP in high alpha and low beta bands (12-13 Hz) resulting in an increase of sensorimotor symptoms and appearance of motor restlessness, behavioral arousals and insomnia. C. Inhibition state is spontaneous relief from sensorimotor symptoms. Short or long-term synaptic plasticities of dopamine receptors towards activations initiate negative feedbacks from inhibitory interneurons. They are supported by inhibitory dopamine modulations- alertness and some awareness generally with regular high alpha EEGs, supraspinal inhibitions and a reverse movement pattern of PLMS during standing up and continuing to walk.

Restless legs syndrome: epidemiological and clinicogenetic study in a South Tyrolean population isolate

Genetic contributions to restless legs syndrome (RLS) have been consistently recognized from population and family studies. To determine the clinical and genetic features of RLS in a population isolate and explore linkage to three previously described susceptibility loci on chromosomes 12q, 14q, and 9p, respectively, an isolated population in the South Tyrolean Alps was identified and 530 adults participated in the study. Using a two-step strategy, 47 patients with idiopathic RLS were ascertained. The prevalence in the population was 8.9%. Twenty-eight patients (59.6%) had at least one affected first-degree relative and were classified as hereditary cases. In a single extended pedigree, linkage to known RLS loci was investigated specifying autosomal dominant and recessive models; parametric and nonparametric multipoint linkage scores were computed. None of the calculated linkage scores was suggestive of linkage between RLS and any of the three investigated loci. This study was conducted in a population isolate providing for a homogeneous genetic and environmental background. The absence of a suggestive linkage signal at the three known RLS susceptibility loci is indicative of further locus heterogeneity of this frequent disorder and encourages further studies to unveil the genetic causes of RLS.

Controversies and challenges in defining the etiology and pathophysiology of restless legs syndrome

Restless legs syndrome (RLS) can occur as a primary disorder, with no apparent cause other than a possible genetic predisposition, or as a secondary condition, most commonly related to iron deficiency, pregnancy, or end-stage renal disease. Recent studies have identified 2 different phenotypes of RLS based on age at onset of symptoms. Persons whose RLS symptoms start at an earlier age (<45 years) are more likely to have a family history of RLS and tend to have a more slowly progressive development of the disorder compared with individuals who have later onset of symptoms. In the past, our ability to determine either prevalence or population factors associated with increased occurrence of RLS has been limited. However, 4 different diagnostic criteria have been established. Familiarity with diagnostic criteria and clinical characteristics are essential for diagnosis and appropriate treatment, if required.

Family-based association study of the restless legs syndrome loci 2 and 3 in a European population

Three loci for the restless legs syndrome (RLS) on chromosomes 12q, 14q, and 9p (RLS1, RLS2, and RLS3) have been mapped, but no gene has been identified as yet. RLS1 has been confirmed in families from three different populations. We conducted a family-based association study of 159 European RLS trios. The subjects were genotyped using microsatellite markers evenly covering the candidate regions on chromosomes 14q and 9p with an average intermarker distance of 1.1 cM. Transmission disequilibrium tests were used to analyze the data, and empirical P values were estimated by permutation testing. On chromosome 14q, a significant association (empirical P = 0.0033) was found with a haplotype formed by markers D14S1014 and D14S1017 when analyzing all families. On chromosome 9p, no significant association in the sample of all families and only marginally significant associations were detected, with a haplotype involving markers D9S1846-D9S171 in a subset of South European trios and with a haplotype at D9S156-D9S157 in a subset of Central European trios (P = 0.0086 and 0.0077, respectively). These results represent the first confirmation of these loci in a mixed European population. Variable results observed in families of different ethnic groups further corroborate the genetic complexity of RLS.

Genetic aspects of restless legs syndrome

Restless legs syndrome (RLS), also known as Ekbom syndrome, is a common movement disorder with sensorimotor symptoms occurring during sleep and quiet wakefulness. The underlying cause for RLS is unknown but genetic influences play a strong part in the pathogenesis of RLS, particularly when the condition starts at a young age. This review explores the genetic basis of RLS and related phenotypic variations. Recently, three loci showing vulnerability to RLS have been described in French-Canadian and Italian families in chromosomes 12q, 14q and 9q, emphasising on an autosomal dominant mode of inheritance. These have been labelled RLS1, RLS2 and RLS3, respectively. However, specific causative mutations remain elusive and no linkage analysis has been identified so far in the candidate genes investigated in RLS.

Ropinirole for the treatment of restless legs syndrome

Dopaminergic agents, anticonvulsants, benzodiazepines, opiates, and iron supplementation comprise the classes of medications commonly used to treat restless legs syndrome (RLS), which is a disorder that is estimated to affect about 1 in 10 individuals worldwide and impacts an affected patient's sleep, mood, daytime function, and quality of life. RLS is characterized by an urge to move the legs that is worse at bedtime and at rest; the symptoms are temporarily relieved by leg movement. It is frequently accompanied by periodic limb movements during sleep (PLMS), which may independently disrupt sleep and may cause daytime drowsiness. Dopaminergic agents are considered to be first-line therapy in the management of RLS as well as PLMS. Ropinirole (Requip((R)), GlaxoSmithKline) is a dopamine agonist that was the first medication approved by the US Food and Drug Administration (FDA) for the treatment of moderate-to-severe primary RLS. Based on several large-scale clinical trials and open-label clinical series, this medication has been demonstrated to be effective and safe in treating the motor symptoms of RLS and improving sleep quality.

Pramipexole: new use for an old drug - the potential use of pramipexole in the treatment of restless legs syndrome

Restless legs syndrome (RLS) is characterized by paraesthesias-dysesthesias and motor restlessness worsening at rest-in the evening, with at least temporary relief by activity. Its etiology is unknown, though it could be secondary to various conditions. It is well known, however, that dopamine plays a crucial role in the pathophysiology of RLS, as dopaminergic agonists achieve marked improvement. Pramipexole is a nonergoline compound with selectivity for D3 dopamine receptors. This drug is very effective in the treatment of idiopathic and secondary RLS and in treatment-resistant patients, as shown by double-blind, placebo-controlled studies in adults. In children, studies are much more limited, and RLS is often misdiagnosed as "growing pain" or attention deficit hyperactivity disorder. Pramipexole has been successful in open studies, eliminating clinical symptoms. This medication has the advantage of being free of the frequently encountered problems seen with ergot derivatives. The side-effects are limited, particularly at the dosages usually prescribed for RLS treatment: They are much lower than in Parkinson's disease, and inappropriate sleepiness and sleep attacks, particularly while driving, or compulsive behavior have not been seen. Compared with the adverse reactions of levodopa, including tolerance, rebound, and augmentation phenomena in RLS, which led to usage of dopamine agonists as first line of treatment for RLS, pramipexole has had one of the best profiles. Augmentation can still be noted with the drug, but after longer usage time compared with many other dopamine agonists. Although excessive daytime sleepiness has been noted, sleep attacks have not been encountered in RLS patients treated with pramipexole.

Linkage analysis identifies a novel locus for restless legs syndrome on chromosome 2q in a South Tyrolean population isolate

Restless legs syndrome (RLS) is a common neurological condition with three loci (12q, 14q, and 9p) described so far, although none of these genes has yet been identified. We report a genomewide linkage scan of patients with RLS (n=37) assessed in a population isolate (n=530) of South Tyrol (Italy). Using both nonparametric and parametric analyses, we initially obtained suggestive evidence of a novel locus on chromosome 2q, with nominal evidence of linkage on chromosomes 5p and 17p. Follow-up genotyping yielded significant evidence of linkage (nonparametric LOD score 5.5, P Collapse

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MESH Headings

• Adolescent
• Adult
• Child
• Chromosome Mapping
• Chromosomes, Human, Pair 2/genetics
• Family
• Female
• Genetic Linkage
• Genetic Predisposition to Disease
• Genome, Human
• Humans
• Italy
• Lod Score
• Male
• Microsatellite Repeats
• Middle Aged
• Pedigree
• Restless Legs Syndrome/genetics

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Affiliation(s)

Irene Pichler Institute of Genetic Medicine, European Academy, Bolzano, Italy
Fabio Marroni
Claudia Beu Volpato
James F Gusella
Christine Klein
Giorgio Casari
Alessandro De Grandi
Peter P Pramstaller

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Association between restless legs syndrome and essential tremor

After observing that several families with essential tremor (ET) clinically cosegregated with restless legs syndrome (RLS), we prospectively evaluated for the presence of RLS in 100 patients presenting to the Baylor College of Medicine with ET and prospectively examined all patients presenting with RLS for the presence of tremor during the same time frame. Of 100 consecutive ET patients (60 women and 75 with a family history of ET) seen over 19 weeks (current age, 65.2 +/- 16.3 years; age at tremor onset, 37.8 +/- 19.9 years) 33 met all criteria for RLS, of which 25 had never been diagnosed previously. A family history of RLS was reported in 57.6% of these 33 patients and was the only significant predictor of RLS in the ET population. Their International Restless Legs Syndrome Rating Scale score was 16.6 +/- 8.1. Over 19 weeks, we also examined 68 consecutive RLS patients (63.2% women and 54.4% with a family history of RLS) for the presence of tremor. Their current age was 55.8 +/- 14.4 years, and age at RLS onset was 33.7 +/- 19.5 years. Overtly pathological tremor was rare, but trace tremor was very common. Overall, we found a very high rate of undiagnosed RLS in patients presenting for tremor, but unlike other "secondary" forms of RLS, this finding was also associated with a high familial history of RLS, suggesting that they share some genetic similarities.

Considering the causes of RLS

The pathophysiology of restless legs syndrome (RLS) is complex and remains to be fully elucidated. The condition is predominantly a disorder of the central rather than the peripheral, nervous system, and dopaminergic dysfunction in subcortical systems appears to play a central role. Conditions associated with secondary RLS, such as pregnancy or end-stage renal disease, are characterized by iron deficiency, which suggests that disturbed iron homeostasis may also play a role in the development of the condition. Although most patients with RLS have normal serum ferritin levels, concentrations of ferritin and transferrin in the cerebrospinal fluid are reduced, suggesting iron deficiency within the central nervous system. Although iron is necessary for the activity of tyrosine hydroxylase, the rate-limiting step in dopamine synthesis, it is unclear whether this relationship plays a role in the aetiology of RLS. There also appears to be a genetic component, particularly when the condition develops before the age of 45 years. Candidate genetic loci have been located on chromosomes 9p, 12q and 14q, but the genes involved have yet to be identified. How these three identified aetiological factors, namely dopaminergic dysfunction, impaired iron homeostasis and genetic disposition, are inter-related in the genesis of RLS remains unclear.

Restless legs syndrome

PURPOSE

The signs and symptoms, epidemiology, etiology, pathophysiology, diagnosis, pharmacologic and nonpharmacologic treatments, and options and guidelines for the treatment of restless legs syndrome (RLS) are reviewed.

SUMMARY

RLS was first described in the 17th century and further characterized in 1945. RLS is a common disorder, occurring in about 10% of the population. Patients with RLS often describe the urge to move, uncomfortable sensations, and pain, which begin or worsen during rest or inactivity such as lying or sitting. Symptoms of RLS make sleeping difficult for many patients, and significant daytime difficulties result from the condition. RLS can either be primary or arise from secondary causes that lead to iron deficiency. There is a familial component in primary RLS, but its underlying mechanisms remain unknown. Of individuals with conditions associated with iron-deficiency states, including pregnancy, renal failure, and anemia, 25-30% may develop RLS. The goals of RLS treatment include improving its symptoms and the patient's quality of life. There are limited data on the treatment of RLS. Pharmacologic therapies include iron replacement, dopaminergic agents (e.g., levodopa), dopamine agonists, anticonvulsants, opioids, and benzodiazepines. There have been no systematic trials of nonpharmacologic therapies for RLS, but good sleep hygiene and avoidance of alcohol, caffeine, and nicotine may improve symptoms.

CONCLUSION

RLS is a common disorder thought to involve abnormal iron metabolism and dopaminergic systems. Nonpharmacologic therapy should be suggested for all patients with RLS, but pharmacologic therapy may be required, and evidence is strongest for levodopa and dopamine agonists.

Undiagnosed individuals with first-degree relatives with restless legs syndrome have increased periodic limb movements

BACKGROUND AND PURPOSE

To evaluate periodic limb movements during sleep (PLMS) in first-degree relatives of both restless legs syndrome (RLS) patients and matched controls without RLS in order to analyze patterns of this motor sign of RLS.

PATIENTS AND METHODS

First-degree relatives of a consecutive case series of RLS patients and matched community controls without RLS were evaluated for diagnosis of primary RLS and for PLMS as determined by a leg activity meter. The data were analyzed to determine whether or not PLMS rates are higher than expected for RLS subjects in these families, who have mostly milder disease, and family members of early-onset RLS patients not themselves diagnosed with RLS.

RESULTS

PLMS activity in family members was significantly higher for those diagnosed as RLS compared to those diagnosed as not-RLS. This difference was greater for older than younger subjects. In family members older than the median study age (52 years old) who were diagnosed as not-RLS, PLMS were significantly more frequent in those related to an early-onset RLS proband than in those related to either a control or late-onset RLS proband.

CONCLUSIONS

PLMS are elevated even in those with mild RLS and reveal an age-related worsening of the motor component of RLS. PLMS may represent an incomplete expression of RLS tendencies in families of patients with early-onset RLS, but this needs to be confirmed in future longitudinal studies. The increase in PLMS with age, reported in healthy controls, may in fact occur in part as a partial expression of familial or genetic factors associated with RLS.

Evidence for further genetic locus heterogeneity and confirmation of RLS-1 in restless legs syndrome

Restless legs syndrome (RLS; MIM 102300) is a common neurological disorder characterized by dysesthesias and an urge to move the lower limbs. The symptoms predominantly occur at rest, in the evening, and improve with movement. There is a high familial aggregation but gene mutations have not yet been found. Three loci for RLS on chromosomes 12q, 14q, and 9p (RLS-1, RLS-2, and RLS-3) have been reported with a recessive (RLS-1) and autosomal dominant (RLS-2, RLS-3) mode of inheritance, respectively. The overall contribution of these loci to this disorder is not known. To evaluate the significance of these loci, we investigated 12 RLS families for possible linkage to these chromosomal regions. Genotyping was carried out in 70 affected family members using 26 polymorphic microsatellite markers (chromosome 12: 7; chromosome 14: 7, chromosome 9: 12). Linkage analysis was carried out using the published parameters applied in the original studies (chromosome 12: q=0.25, f0=0.005, f1=0.005, f2=0.8; chromosome 14: q=0.003, f0=0.005, f1=f2=0.95; chromosome 9: q=0.001, f0=0.005, f1=f2=0.95; affected individuals only). In addition, transmission disequilibrium test (TDT) analyses were done. We found evidence for linkage on chromosome 12 using the TDT. Linkage to RLS-2 and RLS-3 was excluded in 1 of 12 families. This supports the existence of RLS-1 and provides evidence for the likelihood of further genetic locus heterogeneity of RLS. Investigations in additional RLS families are required to confirm the known loci and further genome wide linkage analyses have the potential to identify additional RLS loci.

Restless legs syndrome: a review

Restless legs syndrome (RLS) is a sensorimotor disorder characterized by an irresistible urge to move the limbs accompanied by uncomfortable sensations, leading to sleep disturbances. It is associated with psychiatric comorbidities and a decreased quality of life. RLS is common and most severe among females and the elderly. It may be primary or secondary to other conditions and may be familial. Linkage to several chromosomal loci have been demonstrated. The pathogenesis of RLS involves dopaminergic dysfunction, iron metabolism, and abnormalities in supraspinal inhibition. The mainstay of RLS therapy are dopamine agonists or levodopa. This article reviews the clinical characteristics, epidemiology, diagnosis, pathogenesis, and treatment of RLS.

Genetics of restless legs syndrome

Several studies on restless legs syndrome (RLS) have suggested a substantial genetic contribution in the etiology of this sleep disorder. Clinical surveys of idiopathic RLS patients have shown that 40-90% report a positive family history. The clinical features have been compared between familial and sporadic cases and the only difference found was a younger age-at-onset in familial RLS. Despite several reports suggesting a genetic contribution to the etiology of idiopathic RLS, few molecular genetic studies have been carried out attempting to identify genes that can predispose to this disorder. In particular, genes encoding for the GABA A receptor subunits, the gene for the alpha1 subunit of the glycine receptor, and genes involved in dopaminergic transmission and metabolism have been analyzed, however no significant findings have been reported. Genomewide linkage analysis studies using microsatellite markers have identified three loci for RLS: on chromosome 12q, on chromosome 14q and on chromosome 9p. It is important to investigate whether further RLS families show linkage to one of these loci to discuss the contribution of these loci and to provide a prerequisite of a mutational screening and identification of the RLS genes.

The reliability, validity and responsiveness of the International Restless Legs Syndrome Study Group rating scale and subscales in a clinical-trial setting

PATIENTS AND METHODS

To assess the reliability, validity, and responsiveness of the International Restless Legs Syndrome Study Group's rating scale (the International Restless Legs Scale (IRLS)) (V2.0), using pooled data from two matching, placebo-controlled studies of ropinirole for treating Restless Legs Syndrome (RLS).

RESULTS

Pooled patient samples comprised 550 patients in the baseline (validation) sample and 439 patients in the week 12 longitudinal (responsiveness) sample. Factor analysis revealed acceptability of the IRLS total score (accounting for 40% of the variance) and that nine of the 10 IRLS items could also be assigned to two distinct subscales, the symptoms or symptoms impact subscales. The IRLS total score, symptoms and symptoms impact subscales had acceptable construct validity, internal consistency reliability (alpha=0.81, 0.80, and 0.76, respectively), and concurrent validity (r=-0.68, -0.52, -0.70, respectively, with the Restless Legs Syndrome Quality of Life questionnaire (RLSQoL) overall life impact score). IRLS scores differed significantly between different levels of sleep problems and Clinical Global Impression (CGI) of health status (P<0.0001), indicating known groups and clinical validity, respectively. Changes in scores differed significantly among CGI 'global improvement' levels (P<0.0001), providing evidence of responsiveness.

CONCLUSIONS

The IRLS total score, symptoms, and symptoms impact subscales are reliable, valid, and responsive in a clinical trial setting.

CAG repeats in Restless Legs syndrome

Recent reports established an association of restless legs syndrome (RLS) and spinocerebellar ataxia (SCA) type 1, 2, and 3. To evaluate the contribution of SCA alleles to idiopathic RLS we investigated the CAG repeat length at the SCA1, SCA2, SCA3, SCA6, SCA7, and SCA17 loci in 215 patients who fulfilled the clinical criteria of RLS and presented periodic leg movements in sleep (PLMS) in polysomnographic recording. Fifty percent of patients had a positive family history of RLS. We found one intermediate (CAG)(43) allele for SCA17 in a 44-year-old female with RLS starting at the age of 43. Neurologic examination and family history were unremarkable in this patient. Otherwise, allele distribution did not differ between RLS patients and healthy controls. Stratification for age, age of onset, sex, peripheral neuropathy, and sporadic or familial RLS revealed no effect. Thus, CAG repeat length in the investigated genes is not a major determinant of idiopathic or familial RLS.

Segregation Analysis of Restless Legs Syndrome: Possible Evidence for a Major Gene in a Family Study Using Blinded Diagnoses

OBJECTIVE

The objective of this study was to ascertain the most likely inheritance pattern of restless legs syndrome (RLS) using segregation analysis.

METHODS

Probands were RLS patients presenting to the Neurology and Sleep clinics of the Johns-Hopkins Bayview medical center with willing first and second degree relatives. Blinded diagnosis was made in those who exhibited the four diagnostic features of RLS. Analysis was performed on RLS as a dichotomous trait and considering age of onset models on 590 phenotyped subjects from 77 pedigrees.

RESULTS

All non-genetic models were rejected considering RLS as a dichotomous trait. A single locus Mendelian dominant model with gender as a covariate had best fit with allele frequency of 0.077 and complete penetrance. RLS frequency in non-carrier subjects was estimated to be 0.14. Two underlying distributions of age of onset, with a possible dichotomy at 26.3 years, were identified. Contrary to the results for RLS as a dichotomous trait, age of onset models did not indicate single major gene inheritance.

CONCLUSION

This segregation analysis suggests that the pattern of segregation is consistent with that of a single major locus, when RLS is treated as a dichotomous trait without considering age of onset. The high rate of phenocopies matches known population frequencies and taken with significant residual familial effects and the lack of evidence for a major gene controlling age of onset, indicates that non-genetic causes of RLS may exist and RLS is a complex disorder.

Genetics of restless legs syndrome

Restless legs syndrome (RLS) is a common disorder, although under-diagnosed, with a prevalence of up to 15% depending on the population sampled. Familial aggregation has been widely shown since Ekbom formerly described the condition in 1960; twin studies support a genetic contribution in the development of this disorder. Molecular genetic approaches have identified three genomic regions in RLS susceptibility, however no specific mutations have yet been identified. Herein, we review the current status of genetics in RLS, providing some methodological guidelines to help future research.

Prevalence and Correlates of Restless Legs Syndrome

PURPOSES

The purpose of this analysis was to investigate the prevalence and correlates of restless legs syndrome (RLS) symptoms in the 2005 National Sleep Foundation (NSF) Sleep in America 2005 Poll. The NSF poll is an annual telephone interview of a random, representative sample of US adults.

METHODS

The NSF 2005 poll included 1,506 adults. Their mean age was 49 years, and 775 were women.

RESULTS

Symptoms of RLS that included unpleasant feelings in the legs for at least a few nights a week, which were worse at night, were reported by 9.7% of individuals in this poll, including 8% of men and 11% of women. Those from the northeast United States were much less likely to be at risk than those from other regions of the country (p < 0.05). Those who were unemployed (p < 0.05) or smoked daily (p < 0.5) were more likely to be at risk for RLS, as were those with hypertension, arthritis, gastroesophageal reflux disease, depression, anxiety, and diabetes (p < 0.05 for all). Adults who were at risk for RLS appeared to also be at increased risk for sleep apnea and insomnia (p < 0.05), and were more likely to stay up longer than they planned, to take longer than 30 min to fall asleep, to drive when drowsy, and to report daytime fatigue than those who were not at risk (p < 0.05 for all). They were also more likely to report being late to work, missing work, making errors at work, and missing social events because of sleepiness than other respondents in the poll (p < 0.05 for all).

CONCLUSIONS

RLS is significantly associated with medical and psychiatric conditions, other sleep disorders, unfavorable lifestyle behaviors, and adverse effects on daytime function. Chest physicians who practice sleep medicine need to be able to identify and manage RLS, which is prevalent and is associated with considerable morbidity.

Co-occurrence of restless legs syndrome andParkin mutations in two families

Recent studies have suggested an association between restless legs syndrome (RLS) and Parkinson's disease (PD). We present a large multigenerational family and a smaller family with RLS. A Parkin mutation was found in 10 of 20 patients from both families with idiopathic RLS but was not considered causative. The clinical phenotype did not differ between RLS patients with and without a Parkin mutation. Inheritance of RLS was consistent with autosomal dominant transmission, and linkage analysis excluded all three known loci for RLS.