Iris Melanosis in Cats: Causes, Symptoms, and Treatment Cats.com Despite the name "melanosis," the pigment isn't melanin. The Pigment: It is actually lipofuscin, a "wear and tear" pigment. The Process: Anthraquinone laxatives cause apoptosis (cell death) of the colonic epithelial cells. From melanocytes to melanomas Nature Reviews Cancer Freckle on Lip: Meaning, Causes and Is It Dangerous? (Labial Melanotic Macule) La Bouche Parfaite Oral Melanotic Macule: Symptoms and Treatment Skinsight Melanoma Pictures: Skin Changes and What to Look For