Definition

Flat, pigmented birthmarks on the skin that are light brown in color.

Clinical Details

The genetic mutation overstimulates melanocytes (pigment-producing cells) in specific patches of skin determined by embryonic migration pathways. This results in large, irregularly shaped, light brown marks. In McCune-Albright, these spots often have rough, jagged borders—commonly compared to the coast of Maine—and respect the midline of the body.