Linear and whorled nevoid hypermelanosis (LWNH) is a rare benign condition affecting skin pigment occurring in newborns or early infancy. The primary symptom is swirling streaks of darkened (hyperpigmented) skin, mainly on the trunk and limbs. The dark streaks appear along the lines of normal skin development (lines of Blaschko). LWNH typically spreads for one to two years and then becomes stable. The dark streaks sometimes fade with age. Most of the time, only the skin is affected, but other conditions, such as growth, developmental, or heart problems may be present. The cause for LWNH is unknown. Genetic factors, especially chromosomal mosaicism, may be involved. LWNH is not thought to be inherited. It is diagnosed based on the symptoms. There is no specific treatment for the skin findings in LWNH because they are not associated with any medical problem.

Symptoms may include:

• Swirling streaks of darkened (hyperpigmented) skin
• Developmental delay
• Asymmetric growth
• Cardiovascular defects

The dark skin streaks appear in early infancy and are generally found on the trunk and limbs. The face, palms of the hand, and soles of the feet are not generally affected. The hyperpigmentation may get progress for a few years, and then become stable.. In some people, the darkened skin streaks fade with time. Most people with LWNH have no medical problems related to their condition.

Several chromosome abnormalities have been reported in affected individuals. People with LWNH who have an underlying chromosome abnormality are more likely to have symptoms in addition to those that affect the skin.

Linear and whorled nevoid hypermelanosis (LWNH) generally occurs by chance in people with no family history (sporadically). A few rare cases of LWHN in more than one member of a family have been described.

One specialist who might be involved in the care of someone with LWNH is a dermatologist.

It is unknown how many people have linear and whorled nevoid hypermelanosis. Most of the information on this condition comes from cases described in the medical literature.