Myasthenia gravis


Myasthenia gravis

Description, Causes and Risk Factors:

Abbreviation: MG.

Alternative Name: Goldflam disease.

Myasthenia gravis is a neuromuscular disorder. A disorder marked by fluctuating weakness and fatigue of certain voluntary muscles, including those innervated by brainstem motor nuclei; caused by a marked reduction in the number of acetylcholine receptors in the postsynaptic membrane of the neuromuscular junction, resulting from an autoimmune mechanism.

MG usually is caused by a malfunction of the immune system. The causative factor is unknown, but the disorder may have a genetic link. Causes include a genetic defect, which results in congenital MG, and the circulation of maternal antibodies through the placenta, which result in transient neonatal MG. In some cases, myasthenia gravis may be associated with tumors of the thymus. MG is also characterized by a decrease in number of AChR (acetylcholine receptors).

MG occurs in all races, both genders, and at any age. MG is not thought to be directly inherited nor is it contagious. It does occasionally occur in more than one member of the same family. There are an estimated 50,000 cases of MG in the United States. MG can be found in anyone, but it is "most common in females around the third decade of life."

The disease varies tremendously between individuals, and in any one person the symptoms fluctuate with relapses and remissions. MG can occasionally resolve spontaneously, but for most it is a condition that persists for life. With modern treatments, however, the symptoms can usually be well controlled.

Types: Ocular MG and generalized MG.

Symptoms:

    Fatigue.

  • Drooping of the eyelids.

  • Double vision.

  • Difficulty smiling, speaking, swallowing.

  • Difficulty raising the arms.

  • Difficulty walking.

  • Difficulty breathing if chest muscle are affected.

  • Facial paralysis.

Complications:

  • Respiratory failure.

  • Dysphagia.

Diagnosis:

Differential diagnoses include Lambert Eaton Myasthenic Syndrome, basilar artery thrombosis, amyotrophic lateral sclerosis, brainstem gliomas, cavernous sinussyndromes, dermatomyositis, multiple sclerosis, sarcoidosis, thyroid disease, botulismoculopharyngealmuscular dystrophy.

The history and examination of the patient can suggest the diagnosis but investigations are needed for confirmation.

Test Include:

    The most specific test is to check the blood for the presence of abnormal antibodies using the acetylcholine receptor antibody test. Presence of the antibodies confirms the diagnosis.

  • Another reliable test is the edrophonium chloride test or Tensilon test.

  • Pulmonary function tests.

Imaging studies

    Chest x-ray: Plain anteroposterior and lateral views may identify athymoma as an anterior mediastinal mass.

  • Chest CT scan is mandatory to identify thymoma.

  • MRI of the brain and orbits may help to rule outother causes of cranial nerve deficits but shouldnot be used routinely.

Treatment:

There is no known cure for myasthenia gravis.

Symptomatic treatment include: Medications that enhance the function of the acetylcholine system at the neuromuscular junction.

Medication Options Include:

    Treatment with cholinesterase inhibitors. Side effects include increased sweating, salivation, lacrimation, abdominal cramps, and diarrhea, etc.

  • Treatment with corticosteroids. Side effects include osteoporosis, elevated blood sugars, weight gain, hypertension, peptic ulcer, avascular necrosis of the hip, etc.

  • Treatment with mycophenolate. Side effects include fatigue, increased risk of infection, pancytopenia, increased risk of lymphoma.

  • Treatment with azathioprine. Side effects include flu like symptoms, infections, hepatotoxicity, pancreatitis, myelosuppression, increased risk of lymphoma.

  • Treatment with cyclosporine. Side effects include hepatotoxicity, nephrotoxicity, hypertension, gingival hyperplasia, neuropathy, tremor, increased infections, etc.

  • Treatment with IV Ig. Side effects include acute renal failure, aseptic meningitis, headache, anaphylaxis, pancytopenia.

Surgical removal of the thymus is usually recommended in patients who have a thymoma because the tumour may affect local structures; it does not usually result in improvement in the MG.

Scientists are evaluating new and improving current treatments for MG. Different drugs are being tested, either alone or in combination with existing drug therapies, to see if they are effective in treating the disorder.

Disclaimer:The above information is just informative purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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