An 8-year-old boy, born out of a nonconsanguineous marriage presented with droopy eyelids, bilateral squint since early infancy, and excessive fatigue and weakness on exertion for 3 years. Parents reported an increase in the droopiness of eyelids as the day progressed. Neurological examination revealed bilateral ptosis, complete external ophthalmoplegia, and Cogan's lid twitch sign ([Supplementary Video 1], available in online version), and fatigable weakness of limbs. He had improvement in ptosis on performing the ice pack test. Other cranial nerves, sensory, and cerebellar examinations were normal. A possibility of congenital myasthenic syndrome due to acetylcholine receptor deficiency was considered. Genetic testing revealed a pathogenic homozygous deletion (c.1327del;p.Glu443LysfsTer64) of exon 12 of the CHRNE gene. He was started on pyridostigmine, and on follow-up, he showed gradual improvement of ptosis.

Cogan's lid twitch sign was first described by an American Ophthalmologist, David Glendenning Cogan in 1965.[1] This sign is seen in myasthenia gravis with 50 to 99% sensitivity and 75 to 100% specificity[2] and also reported in dorsal midbrain lesions and Miller Fisher syndrome.[3] [4] The sign is elicited by asking the patient to look downward for 10 to 15 seconds and to return to the primary gaze, and the sign is present when brief twitches of the affected eyelid are seen.[5]