IVIg in myasthenia gravis, Lambert Eaton myasthenic syndrome and inflammatory myopathies: current status

A Unique Case of Non-paraneoplastic Lambert-Eaton Myasthenic Syndrome Treated With Subcutaneous Immunoglobulin: A Case Report and Review of Literature

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune neuromuscular disorder caused by pathogenic autoantibodies directed against voltage-gated calcium channels present on the presynaptic nerve terminal. For LEMS patients refractory to initial symptomatic treatment with amifampridine, immunomodulatory therapy with intravenous immunoglobulin (IVIG) is often utilized. However, in the authors' review of literature, the utility of subcutaneous immunoglobulin (SCIG) in the treatment of LEMS has been scarcely reported. Here, we present a unique case of non-paraneoplastic LEMS managed with SCIG with excellent clinical response and improvement on electromyography. SCIG therapy may be a reasonable alternative for patients with LEMS who do not tolerate the intravenous formulation.

Critical illness-associated weakness and related motor disorders

Weakness of limb and respiratory muscles that occurs in the course of critical illness has become an increasingly common and serious complication of adult and pediatric intensive care unit patients and a cause of prolonged ventilatory support, morbidity, and prolonged hospitalization. Two motor disorders that occur singly or together, namely critical illness polyneuropathy and critical illness myopathy, cause weakness of limb and of breathing muscles, making it difficult to be weaned from ventilatory support, commencing rehabilitation, and extending the length of stay in the intensive care unit, with higher rates of morbidity and mortality. Recovery can take weeks or months and in severe cases, and may be incomplete or absent. Recent findings suggest an improved prognosis of critical illness myopathy compared to polyneuropathy. Prevention and treatment are therefore very important. Its management requires an integrated team approach commencing with neurologic consultation, creatine kinase (CK) measurement, detailed electrodiagnostic, respiratory and neuroimaging studies, and potentially muscle biopsy to elucidate the etiopathogenesis of the weakness in the peripheral and/or central nervous system, for which there may be a variety of causes. These tenets of care are being applied to new cases and survivors of the coronavirus-2 disease pandemic of 2019. This chapter provides an update to the understanding and approach to critical illness motor disorders.

Lambert-Eaton Myasthenic Syndrome

Lambert-Eaton myasthenic syndrome is a paraneoplastic or primary autoimmune neuromuscular junction disorder characterized by proximal weakness, autonomic dysfunction and ariflexia. The characteristic symptoms are thought to be caused by antibodies generated against the P/Q-type voltage-gated calcium channels present on presynaptic nerve terminals and by diminished release of acetylcholine. More than half of Lambert-Eaton myasthenic syndrome cases are associated with small cell lung carcinoma. Diagnosis is confirmed by serologic testing and electrophysiologic studies. 3,4-diaminopyridine is effective symptomatic treatment of LEMS.

Intravenous immunoglobulin in critically ill adults: When and what is the evidence?

Intravenous immunoglobulin (IVIg) use is growing dramatically internationally due to the increasing numbers of acute and chronic conditions that may benefit from IVIg. Patients with conditions that may benefit from IVIg might require intensive care unit (ICU) admission, supporting the need to review IVIg use in the critical care setting. The most common clinical indications for IVIg in adults that may require ICU admission and are commonly supported under clinical practice guidelines are Guillain-Barré syndrome, myasthenia gravis and Lambert-Eaton myasthenic syndrome, inflammatory myopathies, and primary or secondary immunodeficiency diseases complicated by severe bacterial sepsis. Other emerging indications include necrotizing fasciitis, toxic epidermal necrolysis/Stevens-Johnson syndrome, and toxic shock syndrome. The evidence for IVIg use in sepsis and septic shock remains controversial and insufficient to recommend its routine use. Intravenous immunoglobulin is expensive and also carries risks of adverse effects, including common and benign infusion-related reactions, as well as relatively rare and more serious problems, such as thromboembolic events, renal failure, and aseptic meningitis. In this article, we review the literature on conditions requiring ICU admission and IVIg, and we classify them as supported, emerging, or unsupported indications based on the available evidence and guidelines for clinical use of IVIg.

Clinical applications of immunoglobulin in neuromuscular diseases: focus on inflammatory myopathies

During recent years, an increasing number of neuromuscular diseases have been recognized either to be caused primarily by autoimmune mechanisms, or to have important autoimmune components. The involved pathophysiological mechanisms and clinical manifestations have been better recognized and many of these disorders are potentially treatable by immunosuppression or by immunomodulation with intravenous immunoglobulin (IVIg). IVIg has been tried in a variety of immune-mediated neurological diseases, being target of widespread use in central and peripheral nervous systems diseases.

OBJECTIVE

To give an overview of the main topics regarding the mechanism of action and different therapeutic uses of IVIg in neurological practice, mainly in neuromuscular diseases.

Paraneoplastic syndromes: an approach to diagnosis and treatment

Recent medical advances have improved the understanding, diagnosis, and treatment of paraneoplastic syndromes. These disorders arise from tumor secretion of hormones, peptides, or cytokines or from immune cross-reactivity between malignant and normal tissues. Paraneoplastic syndromes may affect diverse organ systems, most notably the endocrine, neurologic, dermatologic, rheumatologic, and hematologic systems. The most commonly associated malignancies include small cell lung cancer, breast cancer, gynecologic tumors, and hematologic malignancies. In some instances, the timely diagnosis of these conditions may lead to detection of an otherwise clinically occult tumor at an early and highly treatable stage. Because paraneoplastic syndromes often cause considerable morbidity, effective treatment can improve patient quality of life, enhance the delivery of cancer therapy, and prolong survival. Treatments include addressing the underlying malignancy, immunosuppression (for neurologic, dermatologic, and rheumatologic paraneoplastic syndromes), and correction of electrolyte and hormonal derangements (for endocrine paraneoplastic syndromes). This review focuses on the diagnosis and treatment of paraneoplastic syndromes, with emphasis on those most frequently encountered clinically. Initial literature searches for this review were conducted using PubMed and the keyword paraneoplastic in conjunction with keywords such as malignancy, SIADH, and limbic encephalitis, depending on the particular topic. Date limitations typically were not used, but preference was given to recent articles when possible.

Sustained response to Rituximab in anti-AChR and anti-MuSK positive Myasthenia Gravis patients

We report the results of treatment with Rituximab in six severe, non-responder MG patients. We treated three AChR+MG and three MuSK+MG patients, representing 2% and 20% of the respective groups of our series. Patients were assessed according to the Myasthenia Gravis Foundation of America (MGFA) recommendations. Antibody titers to AChR and MuSK, Ig levels, and IgG subclasses, were tested before treatment and during a follow-up of 9-22 months. All patients, one class V and five class IVB, improved dramatically, with no side effects. Antibody titers declined in all patients (p=0.006). The decline was significantly better in MuSK+MG patients at 9 months (p=0.046) and correlated with a more sustained clinical improvement. We did not find any significant changes in IgG4 that could explain the different outcome observed between these two groups.

Distinct evolution of calcium channel antibody types in Lambert-Eaton myasthenic syndrome

To determine whether titers of anti-P/Q type and anti-N type calcium channel antibodies provide distinct information, both types of assay were performed during follow-up of 7 patients with Lambert-Eaton myasthenic syndrome (LEMS). In 4 patients with both antibody responses, titers evolved independently and often in an inverse relationship. Two patients with squamous cell lung carcinoma (SqCLC) produced anti-N type channel antibodies, but no detectable anti-P/Q channel responses. These results suggest that anti-N channel autoantibodies constitute an immune response distinct from the anti-P/Q type channel specificity and can also correlate with clinical evolution. Consequently combined assays may provide more comprehensive information during follow-up of LEMS.

Antibodies to AChR, MuSK and VGKC in a patient with myasthenia gravis and Morvan's syndrome

BACKGROUND

A 46-year-old woman presented to a local hospital with acute respiratory failure and a 2-year progressive history of fatigue, personality changes, increased sweating, dysphagia with substantial weight loss, dysarthria, and intermittent ptosis and diplopia. Neurological examination showed facial weakness, lingual atrophy and bulbar palsy, which necessitated the use of a feeding tube and ventilatory support. Mild limb weakness with severe muscle atrophy and diffuse muscle twitches were observed. The patient had also developed visual hallucinations and persecutory delusions. Her personal and family medical histories were unremarkable.

INVESTIGATIONS

Sensory and motor nerve conduction studies, repetitive nerve stimulation, electromyogram, blood-cell counts, general chemistry and metabolic function tests, a CT scan, an [(18)F]fluorodeoxyglucose-PET scan, and tests for serum antibodies to acetylcholine receptors, muscle-specific tyrosine kinase, voltage-gated potassium channels, P/Q-type voltage-gated calcium channels, and paraneoplastic antigens, were carried out.

DIAGNOSIS

Myasthenia gravis associated with antibodies to acetylcholine receptor and muscle-specific tyrosine kinase, and Morvan's syndrome associated with antibodies to voltage-gated potassium channels in the absence of thymoma.

MANAGEMENT

Combined treatment with prednisone, intravenous immunoglobulin, ciclosporin, and rituximab.

Intravenous immunoglobulin therapy in neurological diseases during pregnancy

Immunological changes during pregnancy influence the course of neurological autoimmune diseases in different ways. In case of pregnancy immunomodulatory standard therapies such as interferon-beta, glatiramer acetate,monoclonal antibodies and cytostatics mostly should be discontinued. In those cases intravenous immunoglobulin (IVIg) therapy might be an alternative. In some diseases, contemporary publications describe positive therapeutic effects on the course of disease during or after pregnancy.

IVIG therapy in neurological disorders of childhood

There is growing evidence that intravenous immunoglobulins (IVIG) are effective in some neuroimmunological disorders of childhood. This short review summarizes the evidence-based indications and recommendations of IVIG therapy in these disorders. Despite considerable efforts to define the role and mechanisms of IVIG, more clinical studies are needed to further explore the therapeutic potential of IVIG in childhood diseases of the nervous system and muscle.

Intravenous immunoglobulin therapy in paraneoplastic neurological syndromes

Combining clinical and immunological information, a neurological syndrome can now be diagnosed as a "definite" or "possible" paraneoplastic syndrome according to the newly suggested diagnostic criteria of the PNS Euronetwork. Differentiated diagnosis of a paraneoplastic syndrome is essential for differential therapy in patients. According to the response to IVIG therapy, paraneoplastic disorders may be subgrouped in group A, a clinical response is the rule (prototype Lambert-Eaton myasthenic syndrome), and in group B, IVIG may be helpful in single patients and is indicated in specific clinical settings (prototype anti-Hu associated neurological syndromes). The mode of action of IVIG may range from direct anti-idiotype effect to indirect effects on the cellular part of the pathogenesis of paraneoplastic syndromes. Due to the therapeutic relevance, it is therefore important to diagnose a PND as early as possible, and start immunotherapy including IVIG immediately.

Current usage of intravenous immune globulin and the rationale behind it: the Massachusetts General Hospital data and a review of the literature

BACKGROUND

Intravenous immune globulin (IVIG) has been approved by the Food and Drug Administration (FDA) for use in 6 conditions: immune thrombocytopenic purpura (ITP), primary immunodeficiency, secondary immunodeficiency, pediatric HIV infection, Kawasaki disease, prevention of graft versus host disease (GVHD) and infection in bone marrow transplant recipients. However, most usage is for off-label indications, and for some of these comprehensive guidelines have been published.

STUDY DESIGN AND METHODS

We retrospectively reviewed all approved IVIG transfusions at Massachusetts General Hospital in 2004 to identify the current usage pattern and completed a literature review.

RESULTS

IVIG was most commonly used in the treatment of chronic neuropathy, which included chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy. For such patients, the annual cost of IVIG can exceed 50,000 dollars per patient. Other common indications were the treatment of hypogammaglobulinemia, ITP, renal transplant rejection, myasthenia gravis, Guillain-Barre syndrome, necrotizing fasciitis, autoimmune hemolytic anemia, and Kawasaki disease. IVIG was administered in a variety of other indications each representing <3% of the total treated patients.

CONCLUSION

Only a few indications account for most of the usage for IVIG. Reports concerning IVIG continue to grow at a tremendous pace but few high-quality randomized controlled trials have been reported. Randomized trials are especially needed for conditions such as CIDP, which consume large quantities of product.