Eyelid twitching in MuSK-myasthenia gravis.

A 22-year-old female suffering from MuSK-myasthenia gravis presented with fatigable eyelid ptosis, fluctuated bulbar symptoms and bilateral eyelid twichings which were greatly reinforced after tight closure of eyes and contraction of orbicularis oculi muscles. The patient never received acetylcholinesterase inhibitor treatment. Persistent twichings, irrespectively of clinical status, were signs of cholinergic hyperactivity. MuSK antibodies disrupt MuSK-collagen Q interaction with resultant deficient binding of acetylcholinesterase at synaptic cleft and impaired breakdown of acetylcholine. In myasthenia gravis, clinical signs of cholinergic hyperactivity may point to seropositivity of MuSK antibodies with therapeutic implications in clinical practice.