Rare diseases · Sign or symptom
Marcus Gunn pupil
HP:0200057
What it means
An aberrant pupillary response characterized by (i) Constriction of pupils of both eyes when the light stimulus is applied to the normal eye, and (ii) Dilatation of pupils of both eyes when the light stimulus is rapidly transferred from the normal eye (after brief light exposure to the normal eye) to the affected eye.
Rare diseases that can present with this2
The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.
Part of the broader category
Also called: Relative afferent pupil defect · Relative afferent pupillary defect
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Start free with EleplanThis page uses the Human Phenotype Ontology (2026-06-23) — Human Phenotype Ontology Consortium, hpo.jax.org. Disease associations from Orphanet (INSERM), CC BY 4.0. Content is educational and is not medical advice.