This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
A giant congenital nevus is a dark-colored, often hairy patch of skin that is present at birth (congenital). It grows proportionally to the child. A congenital pigmented nevus is considered giant if by adulthood it is larger than 20cm (about 8 inches) in diameter. Giant congenital nevi can occur in people of any racial or ethnic background and on any area of the body. They result from localized genetic changes in the fetus that lead to excessive growth of melanocytes, the cells in the skin that are responsible for skin color. People with giant congenital nevi may have no other symptoms or may have several symptoms such as fragile, dry, or itchy skin. In about 5% to 10% of the cases the giant congenital nevus is associated with neurocutaneous melanocytosis (excess pigment cells in the brain or spinal cord) and is characterized by neurological symptoms. They also have an increased risk of developing malignant melanoma, a type of skin cancer, especially if the nevus is localized in the vertebral column or when there are multiple associated lesions (satellites).
Whenever possible, treatment includes surgery to remove the nevus. In other cases other treatment such as dermabrasion, shaving or facial excision, chemical peels and laser can be done. In most cases, when there are no neurological problems, the prognosis is good, but it is necessary for the lesions to be examined regularly.
For more information, visit GARD.