Melanosis in Cats

    Melanosis is a condition found in the iris of cats.  Pigment containing cells called melanocytes proliferate causing black spots to appear.  They look like freckles.   If the melanocytes continue to grow, the form larger lesions called nevi.  If multiple nevi form, the condition is called melanosis.  If the disease does not progress any further, the cat will be fine although the color of it’s iris will look different.  Unfortunately, melanosis can convert from benign to malignant requiring immediate enucleation of the affected eye to save the cat.  The problem with melanosis is detecting when the condition is changing from benign to metastatic without being able to take a biopsy sample. 

    Many people confuse melanosis with another pigmented syndrome called lentigo simplex.  The color orange in cats is the result of a genetic mutation on the X chromosome from black/brown to orange.  As orange cats age, the genetic mutation will sometimes mutate back to its original black/brown color causing pigmented spots.  The reverse mutation occurs most commonly on the ears, eyelids, nose and lips of orange cats.  Males and females are both affected.        

Published by kristennelsondvm

Dr. Kristen Nelson grew up on a farm in Watertown, Minn., where she developed a deep love for animals of all kinds. She received a Doctor of Veterinary Medicine degree from the University of Minnesota, College of Veterinary Medicine. Kris then completed a small-animal internship at the prestigious Animal Medical Center in New York City. In addition to writing and speaking, she cares for small and exotic animals in Scottsdale, Az. Dr. Nelson is widely quoted in the media. Her credits include Ladies’ Home Journal, USA TODAY, the Los Angeles Times and numerous radio and television interviews. Dr. Nelson has written two books, Coated With Fur: A Vet’s Life and Coated With Fur: A Blind Cat’s Love. Kris and her husband Steve share their home with rescued cats, birds and a dog.