07. Myasthenia

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Myasthenia gravis [ 39 , 41 , 212 ], also known as myasthenia gravis (MG) ​​Latin [ 219 ] (severe muscle weakness), is a relatively rare chronic autoimmune disease that preferentially affects women [ 178 ].

Myasthenia gravis is linked to a defect in transmission of nerve impulses between nerve endings of motor neurons and muscle fibers [ 219 ]. It is manifested by muscle weakness that worsens with exercise and improves with rest. Its gravity is the risk of respiratory complications [ 69 ] which may involve the prognosis of the patient.

1. Pathophysiology:

Failure of neuromuscular transmission results from blockage of acetylcholine receptors (AChR) at the neuromuscular junction by anti-acetylcholine receptor (anti-AChR AC) [autoantibodies 218 ].

In addition to these humoral factor, it is established that the thymus plays an important role in the pathogenesis of myasthenia gravis [ 187 ]. Approximately 10% of myasthenic carry a thymoma and two patients out of three thymic hyperplasia [ 185 ].

These immune abnormalities may be a genetic carrier [ 220 ], myasthenia gravis appears to be linked to HLA phenotype different depending on whether it is a form of the young woman or a late form.

2. Diagnosis:

In half the cases, the first signs are eye with diplopia (double vision) or ptosis (dropping of the upper eyelids) [ 107 ]. In other cases, the onset is marked by difficulty of phonation, chewing or weakness of the limb muscles.

In myasthenia gravis, muscle weakness increases stress [ 187 ] and can lead to partial paralysis of the muscle. Rest improves muscle strength [ 75 ]. However, in severe forms of the disease, muscle strength is decreased continuously and does not improve even after prolonged rest.

The clinical examination must be completed by the completion of a test anticholinesterase (prostigmine) whose positivity is an important diagnostic argument for myasthenia gravis but negativity does not exclude the diagnosis [ 207 ].

3. Treatment:

Myasthenia gravis can be treated with drugs inhibiting cholinesterase. These drugs prevent the breakdown of acetylcholine and therefore prolongs the duration of action on the acetylcholine receptors of the motor end plate [ 212 ].

If one proceeds thymoma thymectomy. Immunomodulators are sometimes used: infusions of intravenous immunoglobulins and corticosteroids.