Glaucoma · practice question
Mechanism: [READINESS SEED] A child has ptosis with an S-shaped contour of the…
[READINESS SEED] A child has ptosis with an S-shaped contour of the temporal upper lid. The lid feels like a "bag of worms" on palpation, and there are café-au-lait macules on the trunk. What is the most likely mechanism of this child's ptosis?
Show the answer and explanationAnswer and explanation
Answer: A. Mechanical loading of the lid by the neurofibroma
An S-shaped ptotic lid that feels like a "bag of worms," with café-au-lait macules, indicates a plexiform neurofibroma. The lid droops because the infiltrating mass mechanically weighs it down — a mechanical ptosis — rather than from a weak or dysinnervated levator. Recognizing the mass as the cause is the key resident concept.
Clinical pearl: A plexiform neurofibroma is essentially pathognomonic of neurofibromatosis type 1, so finding the classic S-shaped lid should prompt a look for other features of the syndrome.