Abstract

This paper is a case analysis of myasthenia gravis (MG). In the center of this case, there are pathology and pathophysiology of this health condition. The case includes a detailed review of the disease pathophysiology at the cellular level, the pathophysiology of its clinical manifestations, and a review of the disease progress. A brief analysis of differential diagnoses and treatment methods is performed. Recommendations to nurses regarding the management of MG and the patient education are provided.

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Keywords: myasthenia gravis, MG, neuromuscular junctions (NMJ), autoimmune, acetylcholine, muscular, skeletal, weaknesses, antibodies.

Case Analysis: Myasthenia Gravis

Myasthenia gravis (MG) remains one of the rarest and, at the same time, most challenging autoimmune diseases. It is characterized by a progressive muscle weakness and increased fatigability (Armstrong & Schumann, 2003). MG can be neonatal, acquired and congenital persistent. Neonatal MG is diagnosed among 10-15 percent of children born from the mothers with established MG (Armstrong & Schumann, 2003). Despite a growing body of the empirical literature, the pathophysiology of the disease is surrounded by a scientific controversy. Still, several treatment and management plans are available to patients, giving them some hope to relieve a burden of MG symptoms.

Pathophysiology

Cellular Level

Generally, myasthenia gravis (MG) is a result of an autoimmune attack on the "acetylcholine receptors of post-synaptic neuromuscular junctions, resulting in the loss or dysfunction of acetylcholine receptors inhibiting normal neuromuscular transmission" (Armstrong & Schumann, 2003, p.73). The neuromuscular junction (NMJ) is claimed to be susceptible to this kind of autoimmune attacks. The reason is that.it is rich in ion channels facilitating an access to circulating antibodies (Armstrong & Schumann, 2003). More than two thirds of patients with MG develop their disease because IgG antibodies attack their acetylcholine receptors (Armstrong & Schumann, 2003).

It should be noted that muscle susceptibility to MG varies considerably, depending on NMJ properties (Conti-Fine, Milani, & Kaminski, 2006). The NMJ of extrinsic ocular muscles (EOM) appear to be the most vulnerable ones to the risks of myasthenic weakness (Conti-Fine et al., 2006). The neuromuscular junctions of EOM differ from those in skeletal muscles in several essential ways, making EOM a popular target of autoimmune attacks (Conti-Fine et al., 2006). Their synaptic folds are less prominent. the number of their acetylcholine receptors is fewer, compared with skeletal muscles (Conti-Fine et al., 2006). Consequently, they display an increased frequency of neuronal firing, leading to fatigue (Conti-Fine et al., 2006). At the same time, due to the fact that NMJ in skeletal muscles have greater quintal contents and higher levels of postsynaptic folding, they are better protected from the risks of the myasthenic failure (Conti-Fine et al., 2006).

Anti-acetylcholine antibodies (anti-AChR Abs) impact the quality of neuronal transmission in three distinct ways. Firstly, they bind and activate NMJ complements (Conti-Fine et al., 2006). Secondly, they accelerate the degradation of acetylcholine molecules by the means of antigenic modulation (Conti-Fine et al., 2006). Thirdly, they result into the functional AChR blockage (Conti-Fine et al., 2006). Of these three mechanisms, Conti-Fine et al. (2006) has considered the activation of a complement component to be a primary cause of acetylcholine loss and disruptions in neuromuscular transmissions. Still, the role of other neuronal players should not be ignored. The pathophysiology of myasthenia gravis involves CD4+ T cells, which participate in a synthesis of pathogenic anti-acetylcholine antibodies. These cells interact with B cells, which, in turn, result in the creation of low-affinity anti-AChR antibodies, leading to the subsequent somatic mutations in Ig genes (Conti-Fine et al., 2006). This is why patients with MG have CD4+ T cells in their blood and thymus (Conti-Fine et al., 2006). Recent findings also suggest that NMJ malfunction can be induced by the effects of acetyl cholinesterase on a nicotinic acetylcholine receptor (Brenner et al., 2003). Among patients with myasthenia gravis, several researchers also have detected the accumulation of acetylcholinesterase in serum (Brenner et al., 2003). As a result, lowering AChE-R in blood and the use of targeted mRNA therapeutics could have considerable potentials to alleviate the burden of MG in patients (Brenner et al., 2003).

Pathophysiology of Clinical Manifestations

The clinical signs and symptoms of myasthenia gravis reflect the pathophysiology of the disease. When antibodies attack acetylcholin receptors on a motor end-plate, antibody-antigen autoimmune complexes are formed (Armstrong & Schumann, 2003). These immune complexes induce inflammation, damaging neuron receptors and impairing normal patterns of transmission from nerve to muscle (Armstrong & Schumann, 2003). Such impairments in the neural transmission lead to the progressive loss of strength and fatigue (Armstrong & Schumann, 2003). The main factors responsible for autoimmunity include but are not limited to viruses, hereditary predisposition, psychological reactions to adverse life events and even sudden emotional exacerbations (Armstrong & Schumann, 2003). In many patients with MG, thymus gland is also found to be abnormal. However, the exact mechanism of this pathology is unknown: Armstrong and Schumann (2003) suggest that thymus can be responsible for the autoimmune response that results from the excessive production of thymus hormones. At the same time, Lewis (2013) writes that the history of the thymus-MG relationship dates back to the beginning of the 20th century, but whether thymectomy benefits patients with MG is yet to be clarified.

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Disease Progress

MG usually involves levator palpebrae, followed by extraocular muscles and, in the order of progression, facial muscles, mastication, swallowing, phonation, neck muscles, shoulder muscles, and hip muscles (Armstrong & Schumann, 2003). Muscle weaknesses can be localized or generalized (Armstrong & Schumann, 2003). The rest lessens the symptoms, whereas exercises make them worse. That is why the results of physical examinations during the periods of rest may not produce some relevant diagnostic results (Armstrong & Schumann, 2003). The most common symptoms include diplopia and ptosis, which become evident in the evening after a difficult day. Patients complain that they have difficulties swallowing, smiling, pronouncing words, respiratory problems and dyspnea (Armstrong & Schumann, 2003). The progress is slow, as the muscle weakness progresses, until the failure of respiratory muscles leads to fatality (Armstrong & Schumann, 2003).

Diagnosis

Because of its rare nature, physicians face difficulties with diagnosing MG. The main clinical criteria for diagnosing myasthenia gravis include: muscle weakness, which is peripheral and fluctuating, long or spontaneous, associated with ptosis (Armstrong & Schumann, 2003). The exact algorithm of a diagnosis will depend upon the specific symptoms reported by patients. In case of the generalized weakness, lower and upper motor neuron signs should be ruled out (Armstrong & Schumann, 2003). Among patients with ptosis and diplopia, physicians need to differentiate between pseudo and true ptosis (Armstrong & Schumann, 2003). Other conditions to be included in differential diagnosis are: polymyositis, chronic fatigue syndrome, multiple sclerosis, neurasthenia, myopathies, botulism, myotonic dystrophy, retro-orbital tumors, Guillan-Barre, brain tumors, pernicious anemia, cranial nerve lesions, thyrotoxic ophtalmopathy, progressive external ophthalmoplegia and oculopharyngeal myopathy (Armstrong & Schumann, 2003; Lantsova & Sepp, 2005). Diagnostic tests to be used include: an edrophonium test, antibody testing, electrophysiological testing and radiographic testing (Armstrong & Schumann, 2003).

Treatment

New therapies are developed to address the specific autoimmune conditions of MG. Monoclonal antibodies create a basis for the development of treatments to address the immune response (Lewis, 2013). Rituximab and Ofatumumab act against CD 20 molecule, whereas B-cell activating factors (BAFF) are used to break the immune process involved in MG (Lewis, 2013). More common treatments involve anticholinesterase medications, which impact the breakdown of acetylcholine responsible for the autoimmune pathogenesis in MG (Armstrong & Schumann, 2003). Corticosteroids are administered to patients with uncontrolled pyridostigmine, whereas cyclosphorine inhibits T-helper cells and enhances immunosuppression (Armstrong & Schumann, 2003). Plasmopheresis is used to remove acetylcholine antibodies from patients' plasma. Intravenous immunoglobulin acts in a similar fashion (Armstrong & Schumann, 2003). Patients should be educated to avoid excessive stresses, pressures and certain medications, as well as to know how to identify the symptoms of crisis and manage their muscle weakness on a daily basis.

Conclusion

Myasthenia gravis (MG) represents one of the biggest diagnostic and treatment challenges to nurses. MG is an autoimmune condition, whose pathophysiology is based on the autoimmune attacks on neuromuscular junctions. The autoimmune blockage of acetylcholine receptors plays one of the central roles in the development of MG. The current state of nursing science provides numerous treatment recommendations for myasthenia gravis. Still, nurses should be ready to educate their patients about the symptoms, a progress, outcomes and principles of managing this disease.

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