Heterochromia iridis is a condition characterized by abnormalities of the iris (the colored part of the eye).
In people affected by complete heterochromia, the iris of one eye is a different color than the iris of the other eye. Segmental heterochromia occurs when areas of the same iris are different in color. Most cases of heterochromia iridis occur sporadically and are not associated with any other symptoms or problems. Rarely, heterochromia iridis is part of a congenital (present from birth) syndrome such as Waardenburg syndrome, Sturge-Weber syndrome, Parry-Romberg syndrome, or Horner’s syndrome.
Eye color is determined by the concentration and distribution of melanin (a pigment) in the iris. A variety of genetic and acquired (non-genetic) factors influence the final outcome and continued maintenence of the iris color.
Most cases of heterochromia iridis occur sporadically and are not associated with any additional symptoms or health problems. Acquired factors that may lead to heterochromia iridis include:
- Injury or trauma to the eye
- Melanoma of the eye
- Treatment of glaucoma with certain medications such as Latanoprost or Bimatoprost
Rarely, heterochromia iridis may be part of a congenital (present from birth) syndrome, such as Waardenburg syndrome, Sturge-Weber syndrome, congenital Horner’s syndrome, or Parry-Romberg syndrome. Waardenburg syndrome (due to mutations in many different genes) and Sturge-Weber syndrome (due to somatic mutationsin the GNAQ gene) have genetic causes. The exact underlying cause of Horner’s syndrome and Parry-Rombery syndrome is currently unknown. Later-onset cases of heterochromia iridis may be associated with a syndrome called Fuchs heterochromic iridocyclitis, which also has an unkown cause.
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