Associated autoimmune diseases in patients with the Lambert-Eaton myasthenic syndrome and their families

Lambert-Eaton myasthenic syndrome

Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disease characterized by proximal muscle weakness, loss of tendon reflexes, and autonomic dysfunction. Muscle weakness usually starts in the upper legs and can progress to oculobulbar and in severe cases respiratory muscles. P/Q-type voltage-gated calcium channels (VGCCs) localized in the presynaptic motor nerve terminal and in the autonomic nervous system are targeted by antibodies in LEMS patients. These antibodies can be detected in about 90% of patients, and the presence of decrement and increment upon repetitive nerve stimulation is also a highly sensitive diagnostic test. Rapid diagnosis is important because of the association with SCLC in 50%-60% of patients, which stresses the need for vigorous tumor screening after diagnosis. Clinical parameters can predict tumor probability and guide frequency of tumor screening. Treatment of the tumor as well as symptomatic treatment and immunosuppression can effectively control symptoms in the majority of patients.

Type 3 autoimmune polyglandular syndrome (APS-3) or type 3 multiple autoimmune syndrome (MAS-3): an expanding galaxy

BACKGROUND

The number of recognised distinct autoimmune diseases (AIDs) has progressively increased over the years with more than 100 being reported today. The natural history of AIDs is characterized by progression from latent and subclinical to clinical stages and is associated with the presence of the specific circulating autoantibodies. Once presented, AIDs are generally chronic conditions. AIDs have the tendency to cluster and co-occur in a single patient. Autoimmune thyroid diseases (AITD) are the most prevalent of AIDs in the world population, and about one-third of the AITD patients also present with a non-thyroid AID during their life-span. Furthermore, patient with non-thyroid AIDs often presents with a form of AITD as a concurrent condition. Many of the clusters of AIDs are well characterized as distinctive syndromes, while some are infrequent and only described in case reports.

PURPOSE

In this review, we describe the wide spectrum of the combinations and the intricate relationships between AITD and the other AIDs, excluding Addison's disease. These combinations are collectively termed type 3 Autoimmune Polyglandular Syndrome (APS-3), also called type 3 Multiple Autoimmune Syndrome (MAS-3), and represent the most frequent APS in the world populations.

CONCLUSIONS

Numerous associations of AITD with various AIDs could be viewed as if the other AIDs were gravitating like satellites around AITD located in the center of a progressively expanding galaxy of autoimmunity.

Progressive motor quadriparesis with wasting: a diagnostic conundrum

The case of a man in his early 30s, presenting with slowly progressive, asymmetrical onset, pure motor quadriparesis over 9 months with bulbar involvement, absence of upper motor neuron features and significant weight loss, is reported. In view of presentation with diffuse lower motor neuron involvement of short duration, the diagnostic possibilities are discussed. Apart from motor neuron disease, its mimics including muscle and neuromuscular junction disorders were also considered and evaluated for. Carefully assessed clinical and electrophysiological markers which finally clinched the diagnosis of the rare disorder Lambert-Eaton myasthenic syndrome are elaborated. In the present context, recognition of the oddities on clinical and laboratory evaluation is of paramount importance to rule in causes of pure motor quadriparesis.

Lambert-Eaton myasthenic syndrome in a young girl

Lambert-Eaton Myasthenic Syndrome (LEMS) is a neuromuscular junction defect that results in weakness. It is rarely seen in children and most commonly is associated with small-cell lung cancer. Diagnosis of LEMS requires characteristic electromyogram (EMG) findings and the detection of antibodies directed against voltage-gated calcium channels. We report the case of an 8-year-old female child who presented with profound weakness found to have EMG evidence of a neuromuscular junction defect and detectable antivoltage-gated calcium channel antibodies. She received plasma exchange electrophoresis, intravenous immunoglobulin, oral steroids and amifampridine with some clinical improvement. We present a case of a child with a demonstrated autoimmune propensity and no evidence of malignancy, thereby adding to the 12 previously reported cases of LEMS in children.

Presynaptic Paraneoplastic Disorders of the Neuromuscular Junction: An Update

The neuromuscular junction (NMJ) is the target of a variety of immune-mediated disorders, usually classified as presynaptic and postsynaptic, according to the site of the antigenic target and consequently of the neuromuscular transmission alteration. Although less common than the classical autoimmune postsynaptic myasthenia gravis, presynaptic disorders are important to recognize due to the frequent association with cancer. Lambert Eaton myasthenic syndrome is due to a presynaptic failure to release acetylcholine, caused by antibodies to the presynaptic voltage-gated calcium channels. Acquired neuromyotonia is a condition characterized by nerve hyperexcitability often due to the presence of antibodies against proteins associated with voltage-gated potassium channels. This review will focus on the recent developments in the autoimmune presynaptic disorders of the NMJ.

Accuracy of patient-reported data for an online patient registry of autoimmune myasthenia gravis and Lambert-Eaton myasthenic syndrome

Disorders of the neuromuscular junction (NMJ) comprise a spectrum of rare diseases causing muscle fatigability and weakness, leading to life-long effects on quality of life. We established the Dutch-Belgian registry for NMJ disorders, based on a unique combination of patient- and physician-reported information. Information on natural course, disease burden, prevalence of complications and comorbidity is collected through patient-reported standardized questionnaires and verified using medical documentation. Currently, the registry contains information of 565 Myasthenia Gravis (MG) patients and 38 Lambert-Eaton myasthenic syndrome (LEMS) patients, constituting approximately 25% (MG) and 80% (LEMS) of patients in the Netherlands. This is a very large registry, with the highest participation rate per capita. In addition to confirming many disease characteristics previously described in the literature, this registry provides several novel insights. The reported rate of potentially corticosteroid-related comorbidity, including hypertension, heart disease, osteoporosis and type 2 diabetes was high, emphasizing the need to commence corticosteroid-sparing immune suppressive treatment as soon as possible. The reported rate of other auto-immune diseases is far higher than previously expected: 27% of MG and 38% of LEMS patients, and a surprisingly high number of MG patients (47%) is unaware of their antibody status. In conclusion, this registry provides a valuable collection of information regarding MG and LEMS disease course. Continuous collection of annual follow-up data will provide further longitudinal insights in disease burden, course and treatment effect.

Use of therapeutic plasma exchange for pediatric neurological diseases

Therapeutic plasma exchange is used to treat neurological diseases in the pediatric population. Since its first use in pediatric patients with hepatic coma in the form of manual whole blood exchange, therapeutic plasma exchange has been increasingly used to treat these disorders of the nervous system. This expansion is a result of improved techniques and apheresis instruments suitable for small children, as well as the recognition of its applicability to many diseases in the pediatric population. This review provides a historical overview of the use of therapeutic apheresis in children and highlights the most common applications for therapeutic plasma exchange to treat neurological disorders in children.

Beatmung bei neuromuskulären Erkrankungen

Neuromuskuläre Erkrankungen betreffen das erste und zweite Motoneuron, die peripheren Nerven, die neuromuskulären Übertragung und die Muskelzelle. Es handelt sich um eine heterogene Gruppe von erblichen, degenerativen und autoimmunen Erkrankungen. Eine korrekte diagnostische Einordnung ist erforderlich, da zentralnervöse, kardiale, endokrine und weitere Begleitsymptome vorliegen können und für einige Erkrankungen bereits medikamentöse Therapien zur Verfügung stehen. Neuromuskuläre Erkrankungen haben eine große Bedeutung in der neuromuskulären Beatmungsmedizin. Die respiratorische Symptomatik resultiert in der Regel aus Paresen der am Atmen, Schlucken oder Husten beteiligten Muskulatur mit konsekutiver ventilatorischer Insuffienz, Dysphagie bis hin zur Speichelaspiration und Sekretretention. Mittels eines strukturierte Sekretmanagements und einer effektive nichtinvasive oder invasive Beatmungstherapie können neuromuskuläre Patienten viele Jahre mit guter Lebensqualität überleben. Themen dieses Kapitels sind ein Überblick über die neuromuskulären Erkrankungen, die Indikationen und Strategien der nichtinvasiven und der invasiven Beatmung und eine ausführliche Darstellung beatmungsmedizinisch besonders relevanter neuromuskulärer Erkrankungen wie der amyotrophe Lateralsklerose, des Guillain-Barré-Syndroms, der Myasthenia gravis und der Critical-Illness-Polyneuropathie/-Myopathie.

Recent Advances and Therapeutic Options in Lambert-Eaton Myasthenic Syndrome

Lambert-Eaton Myasthenic Syndrome (LEMS) is an autoimmune-mediated neurological disorder that manifests as muscle fatigue, diminished tendon reflexes, with symptoms of cholinergic overactivity. It can be associated with certain neoplastic conditions, the most common being small cell lung carcinoma (SCLC). The basic pathophysiology involved is antibody-mediated targeting of voltage-gated calcium channels (VGCC), which decreases the release of acetylcholine in the synaptic junction. Multiple treatment options have been introduced in the past and, recently, a new drug, amifampridine, has been approved by the Food and Drug Administration (FDA) for the treatment of weakness associated with these patients. We summarize this newly introduced drug with a brief description of other treatment options available.

Lambert-Eaton myasthenic syndrome in a 13-year-old girl with Xp11.22-p11.23 duplication

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disease of the presynaptic neuromuscular junction, typically occurring in adults as a paraneoplastic syndrome. Only rare cases have been reported in childhood. In most childhood cases, malignancies have not been detected but a propensity to autoimmune disease was noticed. Nevertheless, little is known about genetic factors that may contribute to the susceptibility of an individual to develop LEMS. We report on a 13-year-old girl, known with the Xp11.22-p11.23 duplication syndrome, who presented with severe non-paraneoplastic LEMS. The potential role of this microduplication syndrome in the development of LEMS is explored. Previous literature review of twelve Xp11.2 duplication syndrome patients showed that three of them suffered from various autoimmune diseases. The common duplicated region in those three patients and the presented case comprises 12 disease-associated genes including the FOXP3 (Forkhead Box P3) and WAS (Wiskott-Aldrich syndrome) gene, both implicated in immune function. However, it is unclear whether increased gene dosage of one or both of these genes can cause susceptibility to autoimmune diseases. In conclusion, the presented case emphasizes that autoimmune disease is a recurrent feature of the Xp11.2 duplication syndrome, which should be considered in the follow-up of these patients. The exact mechanism underlying this autoimmune propensity remains to be elucidated.

SOX1 antibodies in Lambert-Eaton myasthenic syndrome and screening for small cell lung carcinoma

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder of the neuromuscular synapse. About half of LEMS patients have an associated small cell lung carcinoma (SCLC), which is usually detected after diagnosis of LEMS. This short review summarizes clinical and serological markers shown to predict the presence of SCLC in LEMS patients. SOX1 antibodies are a specific marker for SCLC-LEMS but they are also found in SCLC patients without paraneoplastic neurological syndromes. No relation to any clinical characteristic or survival effect has been found for SOX1-positive patients. Several clinical markers also discriminate between SCLC-LEMS and nontumor LEMS. Detailed analysis of these clinical and demographic characteristics from two independent patient cohorts has led to development of the DELTA-P score. This prediction model has provided for a simple clinical tool to indicate the presence of SCLC early in the course of the disease. The DELTA-P score can be used to guide tumor screening in individual patients.

Lambert-Eaton myasthenic syndrome: from clinical characteristics to therapeutic strategies

Lambert-Eaton myasthenic syndrome (LEMS) is a neuromuscular autoimmune disease that has served as a model for autoimmunity and tumour immunology. In LEMS, the characteristic muscle weakness is thought to be caused by pathogenic autoantibodies directed against voltage-gated calcium channels (VGCC) present on the presynaptic nerve terminal. Half of patients with LEMS have an associated tumour, small-cell lung carcinoma (SCLC), which also expresses functional VGCC. Knowledge of this association led to the discovery of a wide range of paraneoplastic and non-tumour-related neurological disorders of the peripheral and central nervous systems. Detailed clinical studies have improved our diagnostic skills and knowledge of the pathophysiological mechanisms and association of LEMS with SCLC, and have helped with the development of a protocol for early tumour detection.

Long-term disease history, clinical symptoms, health status, and healthcare utilization in patients suffering from Lambert Eaton myasthenic syndrome: Results of a patient interview survey in Germany

INTRODUCTION

The burden of disease in Lambert-Eaton myasthenic syndrome (LEMS) patients is unclear. This study focused on the patient's perspective to obtain patient-reported information on clinical symptoms, burden of illness, impact of LEMS on activities of daily living (ADL), and management of LEMS.

METHODS

Semi-structured, face-to-face interviews with LEMS patients from two specialized centres in Germany between September and December 2010.

RESULTS

Twelve patients participated; mean age 66.7 ± 9.8 years. First symptoms occurred at age 52.5 ± 14.0 years. Mean time between first symptoms and diagnosis was 4.4 ± 6.2 years. Patients reported neuromuscular, cranial, and autonomic symptoms plus general fatigue. Two-thirds of patients reported 10 or more symptoms. The most frequent symptoms were leg weakness (91.7%) and general fatigue (83.3%). Restrictions in ADL were reported always or often in 75% of patients. Over half of the patients (n = 7) reported poor or very poor health status. Mean EQ-5D utility scores were 0.34 ± 0.35, with little day-to-day variation. Patients visited a number of different clinicians; most had been hospitalized at some point in the course of their disease. The most frequent drug treatments were 3,4-diaminopyridine (3,4-DAP) (83.3%) and pyridostigmine (41.5%). The study has several limitations, including small sample size and the potential influence of recall bias.

CONCLUSION

LEMS patients report long individual disease histories. Most patients suffer multiple symptoms which are frequently severe and troublesome, and almost all are restricted in ADL with poor health status. There is high utilization of healthcare resources from diagnosis to ongoing treatment. Physicians should be aware of this rare disease to ensure that patients receive an early diagnosis and prompt and appropriate treatment.

Associated autoimmune diseases in patients with multifocal motor neuropathy and their family members

Multifocal motor neuropathy (MMN) is a rare immune-mediated disorder and is characterized by male predominance, the presence of serum anti-GM1 IgM antibodies in up to half of all patients, responsiveness to intravenous immunoglobulins (IVIg) and an increased frequency of HLA type HLA-DRB1*15. The aim of this study was to assess whether the frequency of autoimmune diseases (AID) is increased in patients with MMN and their first-degree family members, since this would indicate that MMN shares pathogenic mechanisms with other AID. We conducted a case–control study using questionnaires to evaluate the prevalence of AID in MMN and controls, and their first-degree relatives. Questionnaires from 81 MMN patients (417 first-degree relatives) and 438 controls (2,377 first-degree relatives) were analyzed. Overall prevalence of AID was higher in MMN patients (11%) than in controls (5%) (OR 2.4, 95% CI 1.1–5.5, p = 0.037). Type 1 diabetes, Hashimoto’s thyroid disease, and celiac disease were significantly more prevalent in family members of patients than controls. The presence of an additional AID was not associated with age at MMN onset, disease duration, titer of serum anti-GM1 IgM antibodies or HLA type HLA-DRB1*15. The higher frequency of AID in patients with MMN indicates a common autoimmune diathesis.

Lambert-eaton myasthenic syndrome

Lambert Eaton myasthenic syndrome (LEMS) is a rare neuromuscular junction disease. Often, the signs and symptoms of LEMS are mistaken for myasthenia gravis and therefore the workup is misdirected. A physician must look for an occult malignancy when the diagnosis is made and then continue to search for a malignancy for at least 5 years after diagnosis. The diagnosis of LEMS can be confirmed with electrophysiologic studies or with serum calcium channel antibodies. In most patients with LEMS, 3,4-diaminopyridine will improve strength. In patients without malignancy, immunosuppressants do have a role in the treatment of LEMS. Patients and physicians must be aware that certain situations and drugs may exacerbate weakness.

Clinical experience and laboratory investigations in patients with anti-NMDAR encephalitis

Since its discovery in 2007, the encephalitis associated with antibodies against the N-methyl-D-aspartate receptor (NMDAR) has entered the mainstream of neurology and other disciplines. Most patients with anti-NMDAR encephalitis develop a multistage illness that progresses from psychosis, memory deficits, seizures, and language disintegration into a state of unresponsiveness with catatonic features often associated with abnormal movements, and autonomic and breathing instability. The disorder predominantly affects children and young adults, occurs with or without tumour association, and responds to treatment but can relapse. The presence of a tumour (usually an ovarian teratoma) is dependent on age, sex, and ethnicity, being more frequent in women older than 18 years, and slightly more predominant in black women than it is in white women. Patients treated with tumour resection and immunotherapy (corticosteroids, intravenous immunoglobulin, or plasma exchange) respond faster to treatment and less frequently need second-line immunotherapy (cyclophosphamide or rituximab, or both) than do patients without a tumour who receive similar initial immunotherapy. More than 75% of all patients have substantial recovery that occurs in inverse order of symptom development and is associated with a decline of antibody titres. Patients' antibodies cause a titre-dependent, reversible decrease of synaptic NMDAR by a mechanism of crosslinking and internalisation. On the basis of models of pharmacological or genetic disruption of NMDAR, these antibody effects reveal a probable pathogenic relation between the depletion of receptors and the clinical features of anti-NMDAR encephalitis.

Cellular and synaptic mechanisms of anti-NMDA receptor encephalitis

We recently described a severe, potentially lethal, but treatment-responsive encephalitis that associates with autoantibodies to the NMDA receptor (NMDAR) and results in behavioral symptoms similar to those obtained with models of genetic or pharmacologic attenuation of NMDAR function. Here, we demonstrate that patients' NMDAR antibodies cause a selective and reversible decrease in NMDAR surface density and synaptic localization that correlates with patients' antibody titers. The mechanism of this decrease is selective antibody-mediated capping and internalization of surface NMDARs, as Fab fragments prepared from patients' antibodies did not decrease surface receptor density, but subsequent cross-linking with anti-Fab antibodies recapitulated the decrease caused by intact patient NMDAR antibodies. Moreover, whole-cell patch-clamp recordings of miniature EPSCs in cultured rat hippocampal neurons showed that patients' antibodies specifically decreased synaptic NMDAR-mediated currents, without affecting AMPA receptor-mediated currents. In contrast to these profound effects on NMDARs, patients' antibodies did not alter the localization or expression of other glutamate receptors or synaptic proteins, number of synapses, dendritic spines, dendritic complexity, or cell survival. In addition, NMDAR density was dramatically reduced in the hippocampus of female Lewis rats infused with patients' antibodies, similar to the decrease observed in the hippocampus of autopsied patients. These studies establish the cellular mechanisms through which antibodies of patients with anti-NMDAR encephalitis cause a specific, titer-dependent, and reversible loss of NMDARs. The loss of this subtype of glutamate receptors eliminates NMDAR-mediated synaptic function, resulting in the learning, memory, and other behavioral deficits observed in patients with anti-NMDAR encephalitis.

Antibodies to the GABA(B) receptor in limbic encephalitis with seizures: case series and characterisation of the antigen

BACKGROUND

Some encephalitides or seizure disorders once thought idiopathic now seem to be immune mediated. We aimed to describe the clinical features of one such disorder and to identify the autoantigen involved.

METHODS

15 patients who were suspected to have paraneoplastic or immune-mediated limbic encephalitis were clinically assessed. Confocal microscopy, immunoprecipitation, and mass spectrometry were used to characterise the autoantigen. An assay of HEK293 cells transfected with rodent GABA(B1) or GABA(B2) receptor subunits was used as a serological test. 91 patients with encephalitis suspected to be paraneoplastic or immune mediated and 13 individuals with syndromes associated with antibodies to glutamic acid decarboxylase 65 were used as controls.

FINDINGS

All patients presented with early or prominent seizures; other symptoms, MRI, and electroencephalography findings were consistent with predominant limbic dysfunction. All patients had antibodies (mainly IgG1) against a neuronal cell-surface antigen; in three patients antibodies were detected only in CSF. Immunoprecipitation and mass spectrometry showed that the antibodies recognise the B1 subunit of the GABA(B) receptor, an inhibitory receptor that has been associated with seizures and memory dysfunction when disrupted. Confocal microscopy showed colocalisation of the antibody with GABA(B) receptors. Seven of 15 patients had tumours, five of which were small-cell lung cancer, and seven patients had non-neuronal autoantibodies. Although nine of ten patients who received immunotherapy and cancer treatment (when a tumour was found) showed neurological improvement, none of the four patients who were not similarly treated improved (p=0.005). Low levels of GABA(B1) receptor antibodies were identified in two of 104 controls (p<0.0001).

INTERPRETATION

GABA(B) receptor autoimmune encephalitis is a potentially treatable disorder characterised by seizures and, in some patients, associated with small-cell lung cancer and with other autoantibodies.

FUNDING

National Institutes of Health.

Thyrotoxic myopathy mimicking myasthenic syndrome associated with thymic hyperplasia

A 41-year-old man with progressive limb weakness manifested fluctuating muscle weakness as seen in myasthenia gravis (MG). Laboratory investigations revealed hyperthyroidism without the complication of MG. Electrophysiological studies demonstrated abnormal features of neuromuscular transmissions resembling those of the Lambert-Eaton myasthenic syndrome rather than those of MG. A CT scan showed a mediastinal mass that suggested thymic hyperplasia which often complicates MG or hyperthyroidism. Medical treatment of hyperthyroidism resulted in resolution of MG-like symptoms and regression of thymic hyperplasia on CT concomitant with normalization of thyroid function. This case highlights the fact that careful investigations are needed to differentiate MG-like symptoms from genuine MG in cases of hyperthyroidism with thymic lesions.

Perioperative care of patients with neuromuscular disease and dysfunction

A variety of different pathologies result in disease phenotypes that are summarized as neuromuscular diseases because they share commonalty in their clinical consequences for the patient: a progressive weakening of the skeletal muscles. Distinct caution and appropriate changes to the anesthetic plan are advised when care is provided during the perioperative period. The choice of anesthetic technique, anesthetic drugs, and neuromuscular blockade always depends on the type of neuromuscular disease and the surgical procedure planned. A clear diagnosis of the underlying disease and sufficient knowledge and understanding of the pathophysiology are of paramount importance to the practitioner and guide optimal perioperative management of affected patients.

Paraneoplastic syndromes affecting the nervous system

The paraneoplastic neurologic disorders (PND) are a diverse group of diseases characterized by the presence of neurologic dysfunction in the setting of a remote cancer. PND can affect almost any part of the nervous system, and are most commonly associated with lung cancer (small cell) and gynecologic tumors. Laboratory studies have demonstrated that an autoimmune response links the neurologic disorder and the cancer, and established a model whereby the cancer is believed to initiate the syndrome by expressing a protein antigen normally expressed in the nervous system, leading to anti-tumor immune response followed by autoimmune neurologic symptoms. We review the currently known PND and their pathogenesis.