Overview

• Autoimmune neuromuscular disease characterised by generalised muscle weakness
• Pathophysiology involves autoantibodies against postsynaptic nicotinic Ach receptors (AChR) at the neuromuscular junction
• F>M
• Associations with thymomas (tumour of anterior mediastinum) and thymic hyperplasia
  • Thymomas may cause superior vena cava obstruction.
• Risk Factors → presence of other autoimmune conditions

Making Diagnosis

Clinical Features:

• Muscle Fatigability → worsens with activity and improves on rest (hence patients typically complain of it being worse at end of day)
• Ptosis (droopy eyelid) + Diplopia (double vision)
• Dysphagia → difficulty swallowing
• Dysarthria → changes in speech
• Facial Paresis
• Proximal Limb Weakness
• Respiratory Muscle Weakness → may lead to dyspnoea

Symptoms may be worsened by beta-blockers. May cause FVC to drop due to respiratory muscle weakness.