Myasthenia Gravis

Question 1

Epidemiology of Myasthenia Gravis

Answer 1

Uncommon, The mean age of onset is 28 years in females and 42 years in males, F > M = 3:2

Question 2

Aetiology

Answer 2

Idiopathic-Immune

Question 3

Pathogensis

Answer 3

Auto antibody destruction of Ach receptors of striated skeletal muscle

Question 4

Natural history

Answer 4

progressive loss of strength

Question 5

Clinical manefestations

Answer 5

The usual initial complaint is a specific muscle weakness Extraocular muscle weakness or ptosis is present initially in 50% of patients and occurs during the course of illness in 90%

The disease remains exclusively ocular in only 16% of patients
Rarely, patients have generalized weakness without ocular muscle weakness

Bulbar muscle weakness is also common, along with weakness of head extension and flexion

Limb weakness may be more severe proximally than distally
Isolated limb muscle weakness is the presenting symptom in fewer than 10% of patients

Weakness is typically least severe in the morning and worsens as the day progresses

Weakness is increased by exertion and alleviated by rest
Weakness progresses from mild to more severe over weeks or months, with exacerbations and remissions

Weakness tends to spread from the ocular to facial to bulbar muscles and then to truncal and limb muscles

About 87% of patients have generalized disease within 13 months after onset

Less often, symptoms may remain limited to the extraocular and eyelid muscles for years

Question 6

Symptoms

Answer 6

diplopia
dysphagia
difficult chewing
dysarthria
weakness in proximal muscles

Question 7

Signs

Answer 7

Ptosis/fascial weakness

Question 8

Complications

Answer 8

Morbidity results from intermittent impairment of muscle strength, which may cause aspiration, increased incidence of pneumonia, falls, and even respiratory failure if not treated. + medication s/e
thymus hyperplasia/malignancy

Question 9

Prognosis

Answer 9

3% mortality, decreased QOL