Differential Diagnosis for a 13-year-old female with a unilaterally dilated pupil
- Single most likely diagnosis:
- Benign physiological anisocoria: This condition is characterized by a small, normal variation in pupil size between the two eyes, which can be more noticeable in certain lighting conditions. It's a common and harmless finding, especially in the absence of other symptoms.
- Other Likely diagnoses:
- Local eye conditions (e.g., iritis, uveitis, or a posterior synechiae causing a sectoral iris palsy): These conditions can cause a unilateral dilated pupil due to inflammation or adhesions within the eye.
- Trauma: Even minor trauma to the eye can cause a dilated pupil on the affected side due to iris sphincter damage or third cranial nerve palsy.
- Pharmacological mydriasis: Accidental or intentional exposure to substances that dilate the pupils (e.g., certain medications, chemicals, or plants) could cause unilateral pupil dilation.
- Do Not Miss diagnoses:
- Third cranial nerve (oculomotor nerve) palsy: This can be caused by serious conditions such as an aneurysm, stroke, or increased intracranial pressure. Although less common in children, it's crucial to rule out these potentially life-threatening causes.
- Horner syndrome: While typically presenting with miosis (pupil constriction), in its early stages or in certain types, there might be anisocoria (unequal pupil sizes) that could be mistaken for a dilated pupil.
- Adie's tonic pupil: A condition that affects the nerves controlling the pupil, leading to a dilated pupil that reacts poorly to light. It's usually benign but can be a sign of underlying autonomic dysfunction.
- Rare diagnoses:
- Congenital conditions (e.g., congenital third cranial nerve palsy, or other rare genetic conditions affecting the eye or nervous system): These are uncommon but should be considered in the differential diagnosis, especially if other signs or symptoms are present.
- Infectious or inflammatory conditions affecting the central nervous system (e.g., neurosyphilis, Lyme disease): These can cause a variety of neurological symptoms, including pupil abnormalities, and are important to consider, especially with a relevant exposure history.