A congenital pigmented or melanocytic nevus is a dark-colored, often hairy patch of skin that is present at birth.
A giant congenital nevus is smaller in infants and children, but it usually continues to grow with the child. A giant pigmented nevus is larger than 8 inches once it stops growing.
Congenital giant pigmented nevus; Giant hairy nevus; Giant pigmented nevus; Bathing trunk nevus; Congenital melanocytic nevus - large
Bathing trunk nevi are thought to be caused by defects or problems that occur as a baby grows in the womb. However, in some families bathing trunk nevi may be inherited.
A bathing trunk nevus may occur with:
Smaller congenital pigmented or melanocytic nevi are common in children and lead to fewer complications. Larger or giant nevi are fairly rare.
A nevus will appear as dark-colored patch with any of the following:
Nevi are commonly found on the upper or lower parts of the back or the abdomen. They may also be found on the:
All birthmarks should be evaluated by your health care provider. A skin biopsy may be taken for examination to determine whether the cells have become cancerous.
An MRI of the brain might be performed if the skin lesion is over the spine. There also may be problems in the brain when a giant nevus is found on the spine.
Treatment involves frequent exams to check for skin cancers.
When possible, surgery to remove the nevus will be done. Skin grafting is done when needed. Larger nevi may need to be removed in several stages.
Lasers and dermabrasion can also be used to improve the appearance. However, using these techniques may not remove the entire birthmark, and may make it harder to diagnose skin cancer (melanoma). For these reasons, surgery is controversial.
Psychological treatment can help with the emotional impact of having a disfiguring disorder.
Skin cancer (such as malignant melanoma and other types) may develop in up to 15% (1 out of 6) of people with larger or giant nevi, often in childhood. The risk is higher for larger or giant congenital nevi located on the back or abdomen.
Rarely, bathing trunk nevi occur with a condition that causes a growth of pigment-producing cells in the head (leptomeningeal melanocytosis). Complications include:
This condition is usually diagnosed at birth. Call for an appointment with your health care provider (or mention it during a well-baby exam) if your child has a large pigmented area anywhere on the skin.
Bett BJ. Large or multiple congenital melanocytic nevi: Occurrence of neurocutaneous melanocytosis in 1008 persons. J Am Acad Dermatol. 2006 May;54(5):767-777.
Congenital melanocytic nevi. In: Habif TP, ed. Clinical Dermatology. 5th ed. Philadelphia, Pa: Saunders Elsevier; 2009:pp 850-851.