Iris Heterochromia in Acquired Horner Syndrome Following Surgical Excision of Parapharyngeal Neuroblastoma.

This report describes an infant who developed iris heterochromia 2 years after presenting at age 2 months with acquired Horner syndrome following excision of a parapharyngeal neuroblastoma. Iris heterochromia is classically associated with congenital, not acquired, Horner syndrome due to a disruption of the oculosympathetic pathway early in life that alters iris melanocyte migration, leading to an ipsilateral lighter colored iris compared to the fellow iris. In the case reported here, the disruption to the oculosympathetic pathway occurred so early in life that normal iris melanocyte migration was impacted on the affected side, leading to eventual iris heterochromia that was noted almost 2 years later.