Hori's nevus

Hori's nevus, also known as acquired bilateral nevomelanocytic nevus or ABNOM, is a type of melanocytic nevus characterized by its acquired nature and symmetrical distribution on the face. Unlike congenital melanocytic nevi, Hori's nevus develops later in life, typically in adult women, and is more common in individuals of Asian descent. This condition is considered benign, but it can cause cosmetic concerns due to its appearance.

Etiology and Pathogenesis

The exact cause of Hori's nevus is not fully understood, but it is believed to be multifactorial. Genetic predisposition, hormonal influences, and sun exposure are thought to play roles in its development. The lesions of Hori's nevus contain an increased number of melanocytes and melanin, suggesting an overactivity of melanin-producing cells in the affected areas.

Clinical Features

Hori's nevus presents as symmetrical, blue-gray or brown patches on the face, especially on the cheeks, nose, and forehead. The lesions are usually flat and do not exhibit textural changes. They tend to appear in adulthood, with a higher prevalence in women, suggesting a possible hormonal influence. Although Hori's nevus is asymptomatic, its appearance can lead to psychological distress in affected individuals.

Diagnosis

Diagnosis of Hori's nevus is primarily clinical, based on the characteristic appearance of the lesions. Dermoscopy can aid in the diagnosis by revealing specific patterns, such as a homogenous blue-gray pigmentation. In uncertain cases, a biopsy may be performed to rule out other pigmented lesions and confirm the diagnosis histologically.

Treatment

Treatment of Hori's nevus is challenging and primarily aimed at cosmetic improvement. Options include laser therapy, such as Q-switched lasers, which can be effective in lightening the lesions. Other treatments, such as chemical peels and topical bleaching agents, have been used with varying degrees of success. It is important for patients to have realistic expectations and understand that complete removal may not be possible.

Prognosis

The prognosis for Hori's nevus is generally good, as it is a benign condition. However, the cosmetic impact can be significant, and some individuals may experience psychological distress due to the appearance of the lesions. Treatment can improve the cosmetic appearance but may require multiple sessions and ongoing maintenance.

Prevention

There are no specific measures to prevent Hori's nevus, but minimizing sun exposure and using sunscreen may help reduce the risk of developing pigmented lesions. Individuals with a family history of Hori's nevus or other pigmented disorders should be particularly cautious about sun protection.