Myasthenia gravis

• immune mediated neuromuscular blockade (anti- Ach receptor antibodies)
• acquired, congenital, and transient neonatal forms
• ptosis, diplopia, facial weakness with feeding problems in infants, limb-girdle weakness
• rapid fatigue of muscles is characteristic
• EMG: diminishing muscle potentials in response to repetitive nerve stimulation
• Tensilon test: transient improvement w/administration of short acting cholinesterase inhibitor
• RX: neostigmine, thymectomy, steroids, IVIG

If mother has MG, Transient Neonatal myasthenia affects 10-20% of children:

• Flatfacies, weak suck, feeble cry, respiratory insufficiency
• Onset 12-48 hours after birth
• Persists up to 15 weeks (mean 3 weeks)
• Normal strength, no increased risk of MG once maternal Ab’s disappear
• Symptoms respond toanticholinesteraseagents
• Rarely present with arthrogryposis

Congenital MG: Rare, Nearly always permanent.

Vs Lambert-Eaton: autoimmune attack directed against the voltage-gated calcium channels on the presynaptic motor nerve terminal.

CHLA Board Review 2005