Myasthenia (miastenia gravis)

Description of the Disease

Myasthenia gravis, an autoimmune neuromuscular junction disease, causes periodic transient muscle weakness and pathological weakness. In this disease, the immune system malfunctions, producing pathological antibodies (lymphocytes against the substance responsible for transmitting nerve signals to the muscle). The incidence rate is 43-48 per million population. Women are affected three times more often than men. About 10% of new cases occur in children under 10 years of age. Peak incidence in women occurs between 20-30 years, and in men between 50-60 years. Myasthenia is divided into ocular myasthenia (15%) and generalized myasthenia (85%).

Symptoms

a) About 40% of cases begin with eye symptoms, including diplopia (double vision) that improves with rest, drooping eyelids, and difficulty lifting them (often affecting one eye more when fatigued). Cold alleviates these symptoms.

b) Speech becomes impaired: a person speaks until their voice becomes quieter and sometimes disappears completely (aphonia); after resting, the voice returns.

c) Facial expression changes, resulting in a crooked smile.

d) Pain-free muscle weakness that intensifies during activity and improves with rest. Eye and neck muscles typically show weakness first, progressing to limb weakness as the disease advances. Breathing, chewing, and swallowing (especially solid foods) may also be affected.

The course of myasthenia fluctuates, with symptoms worsening and then improving. Stress, pregnancy, puberty, emotions, infections, and certain medications (such as verapamil, propranolol, and antibiotics like ciprofloxacin) can trigger worsening.

Diagnosis

Diagnosis is based on clinical symptoms, provocative tests (such as voice disappearance after more than 30 squats or speaking for 3 minutes), electrophysiological studies (measuring nerve impulse conduction to muscles and their response), and drug trials (observing temporary improvement after use). Blood tests check for antibodies. Chest computed tomography examines the thymus, often associated with myasthenia due to its enlargement or presence of a tumor. The thyroid gland is also examined.

Treatment

• Cholinesterase inhibitors (pyridostigmine, neostigmine)
• Thymectomy
• Plasmapheresis (removal of harmful antibodies)
• Immunosuppressants (prednisolone, azathioprine)
• Immunoglobulins

Source | Author Doctor Nikas Samuolis, reviewed by Prof. Virginijus Šapoka | Vilnius University | Faculty of Medicine | Head of the Department of Internal Medicine, Family Medicine, and Oncology