Myasthenia gravis

**Definition:** Myasthenia gravis is the most common acquired auto-antibody mediated neuromuscular transmission disorder. Prevalence is 1–2 per 10,000 persons. Fluctuating weakness increasing with repeated activity and improving after a period of rest is the hallmark. Myasthenia Gravis with antibodies directed against postsynaptic proteins, usually the nicotinic acetylcholine receptor are the most prevalent. Other types are Myasthenia Gravis associated with muscle-specific kinase antibodies and MG with unknown autoantibodies (seronegative) Myasthenia Gravis. There are three groups: 1. Purely ocular Myasthenia Gravis 2. Early-onset (<40-50 years) generalised Myasthenia Gravis 3. Late-onset generalised MG. In about 15%, the disease can be classified as paraneoplastic, usually associated with a thymoma.

**Long definition:** A disorder of neuromuscular transmission characterized by fatigable weakness of cranial and skeletal muscles. Autoantibodies directed against acetylcholine receptors damage the motor endplate portion of the neuromuscular junction, impairing the transmission of impulses to skeletal muscles. Clinical manifestations may include fluctuating diplopia and ptosis, and fatigable weakness of facial, bulbar, respiratory, and proximal limb muscles.