[Drugs that may trigger or exacerbate myasthenia gravis]

Transient Neonatal Myasthenia Gravis: A Case Report

Transient neonatal myasthenia gravis (TNMG) is a neuromuscular disorder that occurs in infants born from mothers with myasthenia gravis (MG) due to transplacental transfer of antibodies against the acetylcholine receptor. TNMG is a rare form occurring in 10-15% of infants born from mothers with MG. We present a case of a newborn with TNMG with generalized hypotonia and respiratory distress. The newborn shows symptoms of hypotonia, weakened reflexes, poor crying, difficult sucking and potentiated tachydyspnea after 24 hours of birth and needs of assisted mechanical ventilation. Based on the mother's positive history of MG and the high titer of mother's (8.43nmol/l) and newborn's (9.088nmol/l) anti-AChR antibodies, TNMG was diagnosed. The baby was treated with assisted mechanical ventilation and neostig-mine until the anti-AChR antibody titer was negative. Adequate management of the newborn resulted in a positive outcome and evident withdrawal of the symptoms. Although TNMG is one of the rare neuromuscular disorders in newborns that can be treated, a multidisciplinary approach in the management of pregnant women with MG and newborns through timely diagnosis and early appropriate treatment, results in successful resolution of this condition.

Statins Neuromuscular Adverse Effects

Statins are drugs widely prescribed in high-risk patients for cerebrovascular or cardiovascular diseases and are, usually, safe and well tolerated. However, these drugs sometimes may cause neuromuscular side effects that represent about two-third of all adverse events. Muscle-related adverse events include cramps, myalgia, weakness, immune-mediated necrotizing myopathy and, more rarely, rhabdomyolysis. Moreover, they may lead to peripheral neuropathy and induce or unmask a preexisting neuromuscular junction dysfunction. A clinical follow up of patients assuming statins could reveal early side effects that may cause neuromuscular damage and suggest how to better modulate their use. In fact, statin dechallenge or cessation, or the alternative use of other lipid-lowering agents, can avoid adverse events. This review summarizes the current knowledge on statin-associated neuromuscular adverse effects, diagnosis, and management. It is conceivable that the incidence of neuromuscular complications will increase because, nowadays, use of statins is even more diffused than in the past. On this purpose, it is expected that pharmacogenomic and environmental studies will help to timely predict neuromuscular complications due to statin exposure, leading to a more personalized therapeutic approach.

Pharmacological Management of Myasthenia Gravis: A Century of Expert Opinions in Cecil Textbook of Medicine

BACKGROUND

Advances in drug therapy for myasthenia gravis have had a significant impact on the quality of life and work potential of a substantial majority of affected persons and has contributed to a remarkable decrease in the frequency and severity of complications, hospitalizations, and mortality.

STUDY QUESTION

What are the milestones of the changes in the expert approach to the pharmacological management of myasthenia in the past century?

STUDY DESIGN

To determine the changes in the experts' approach to the management of myasthenia gravis, as presented in a widely used textbook in the United States.

DATA SOURCES

The chapters presenting the management of myasthenia gravis in the 26 editions of Cecil Textbook of Medicine published from 1927 to 2020.

RESULTS

Adequate feeding, absolute rest in bed, and "tonics" were the only interventions recommended for the care of patients with myasthenia gravis in 1927. Ephedrine and glycine were used in the early 1930s. Treatment with the anticholinesterases physostigmine and neostigmine was recommended in 1937, 3 years after Mary Walker discovered it in the United Kingdom. Immunosuppressant pharmacological interventions with prednisone and azathioprine have been considered the standard since 1975, and intravenous immune globulin was added to usual care in 1996. The newer immunosuppressant drugs mycophenolate, cyclosporine, and tacrolimus have expanded the arsenal since 2008, and the monoclonal antibodies rituximab and eculizumab have been mentioned in the textbooks published in 2012-2020. The first randomized clinical trial of drug therapy for myasthenia gravis was published in 1987.

CONCLUSIONS

The pharmacological management of myasthenia gravis was revolutionized by the epiphany of an astute clinician in the 1930s. Immunosuppressant treatment was a logical step once the autoimmune nature of the condition was established. The major therapeutic advances highlight the values of empiricism and persistent attention to detail in treating relatively rare chronic disorders.

Severe Preeclampsia in the Setting of Myasthenia Gravis

Myasthenia gravis (MG) is a rare autoimmune disease that leads to progressive muscle weakness and is common during female reproductive years. The myasthenic mother and her newborn must be observed carefully, as complications during all stages of pregnancy and the puerperium may arise suddenly. Preeclampsia is a common obstetrical condition for which magnesium sulfate is used for seizure prophylaxis. However, magnesium sulfate is strongly contraindicated in MG as it impairs already slowed nerve-muscle connections. Similarly, many first-line antihypertensive medications, including calcium channels blockers and β-blockers, may lead to MG exacerbation. This case describes the effective obstetrical management of a patient with MG who developed severe preeclampsia. The effective use of levetiracetam and various antihypertensive medications including intravenous labetalol is described. A review of the ten reported cases of MG complicated by preeclampsia is examined to aggregate observations of clinical care, with focus on delivery methods, anticonvulsants, and antihypertensive medications.

Acute Respiratory Failure Induced by Magnesium Replacement in a 62-Year-Old Woman with Myasthenia Gravis

Magnesium is known to act at the neuromuscular junction by inhibiting the presynaptic release of acetylcholine and desensitizing the postsynaptic membrane. Because of these effects, magnesium has been postulated to potentiate neuromuscular weakness. We describe the case of a 62-year-old woman with myasthenia gravis and a metastatic thymoma who was admitted to our intensive care unit for management of a myasthenic crisis. The patient's neuromuscular weakness worsened in association with standard intravenous magnesium replacement, and the exacerbated respiratory failure necessitated intubation, mechanical ventilation, and an extended stay in the intensive care unit. The effect of magnesium replacement on myasthenia gravis patients has not been well documented, and we present this case to increase awareness and stimulate research. In addition, we discuss the relevant medical literature.

Myasthenia gravis masquerading as dysphagia: unveiled by magnesium infusion

Myasthenia gravis (MG) is a neuromuscular disorder that typically affects the ocular, bulbar, neck, proximal limbs and respiratory muscles. Dysphagia can occasionally be the only presenting symptom leading to extensive but ultimately futile gastrointestinal workup. Delay in diagnosis and use of certain pharmacological agents in the interim can lead to a myasthenic crisis, which though diagnostic is life threatening. We document a case of dysphagia as the only symptom of myasthenia, diagnosed after a magnesium infusion precipitated myasthenic crisis. A 70-year-old Caucasian woman who had had progressive dysphagia for 2 years, for which multiple oesophageal dilations were performed. During a hosptalisation for further gastrointestinal workup, she went into myasthenic crisis (respiratory failure) after receiving magnesium replacement. She required ventilatory support and received five plasma exchange (PLEX) treatments after myasthenia was confirmed by the detection of high antiacetylcholine receptor antibody. Though her symptoms improved, she had a prolonged hospital stay (25 days) and required 18 days of mechanical ventilation. This underscores the morbidity associated with a delay in diagnosis of this condition. This case report suggests that neuromuscular causes should be considered early in elderly patients presenting with dysphagia. Timely diagnosis, initiation of management and avoidance of drugs that affect neuromuscular transmission may help reduce the morbidity and mortality associated with myasthenic crisis.