Hori's Naevus – Causes and Treatment Method
What is Hori’s Naevus
Hori's Naevus, also known as acquired bilateral Nevus of Ota - like macules (ABNOM), is a pigmentation disorder that is often mistaken for freckles and birthmarks like Nevus of Ota and Ito. This is due to the appearance of numerous speckled macules, ranging in colour from dark brown to slate grey, over both cheeks. Unlike freckles, which develop on the skin's surface, Hori's Naevus develops in the deeper layers. Therefore, treating it with topical creams will not be effective.
What Causes Hori’s Naevus
Hori's Naevus pigmentation is believed to have a genetic predisposition that worsens with age and prolonged sun exposure. In addition to this, other pigmentation disorders can result from hormonal changes caused by pregnancy and hormonal medication. Although it is prevalent in Asian women, the condition can develop in men too. Individuals living in regions with high UV exposure are prone to developing these pigments, sometimes as early as their 20s.
Ignoring the pigments for a long period of time will lead to a darker pigmentation. As the condition progresses, it will appear on the forehead and nose and will become more confluent, growing and merging into a large area.
Different types of Naevi
There are three different types of naevi that form on the skin: Nevus of Ota, Nevus of Ito, and Hori's Nevus.
Hori's Naevus
Also referred to as acquired bilateral Nevus of Ota-like macules (ABNOM), this pigmentation disorder is frequently confused with freckles and birthmarks such as Nevus of Ota and Nevus of Ito. Unlike Nevus of Ota and Nevus of Ito, which are present from birth or childhood, Hori's Naevus typically develops in older adults.
Nevus of Ota
Also known as Oculomucodermal melanocytosis, this benign dermal melanocytosis typically manifests in facial regions, especially around the eyes. The distinctive grey-blue hyperpigmentation results from melanocytes trapped in the dermis, appearing in areas such as the sclera, cornea, iris, and retina of the eye.
Naevus of Ito
Known as nevus fuscoceruleus acromiodeltoideus, this skin condition shares similarities with Nevus of Ota, but differs in geographic distribution. Nevus of Ito typically manifests as pigmentation on the shoulder and upper arm areas.
How to recognise Hori’s Naevus?
Signs of the condition include multiple speckled macules of blue-brown to slate-grey colour. Essentially, the colour pigment builds up on the cheeks on either side of the face. The condition can also occur in other parts of the body. For example, on the forehead, the nose, and the eyelids. In the early stages of pigmentation, brownish clusters with distinct edges are observed. However, as time passes by, the clusters merge and form bigger and darker patterns on the surface of the skin.
Treatments for Hori’s Naevus
Lasers have been found effective in treating Hori's Naevus, as the skin condition is deep in the dermis. Some of the popular pigmentation lasers include Q-switched nanosecond and picosecond Nd Yag lasers, and the picosecond Alexandrite laser.
These lasers are non-invasive treatments that use a high-intensity pulsed beam light in ultra-short pulse durations. Typically, Q-Switched nanosecond laser beam pulses last one billionth of a second. The picosecond laser operates at one trillionth of a second which is 100 times faster than the nanosecond laser. The energy they generate shatters the pigmentation, which are naturally expelled through the body’s lymphatic processes.
Nd: YAG Laser Treatment
It targets the dark pigments on the skin in affected areas of the body. The Nd: YAG laser operates at specific wavelengths of 532nm and 1064nm which are absorbed by coloured pigments causing the Hori’s naevus or other forms of pigmentation. On absorbing the laser energy, the pigmented cells disintegrate into smaller portions, which are ultimately expelled by the body’s natural excretory mechanism.Picosecond Alexandrite Laser Treatment
These are also engineered for demolishing pigments by emitting energy bursts in the 755m wavelength. Since they work at such high speeds, these lasers generate less thermal energy but more sound energy. The powerful acoustic wave shatters the pigmentation cells and expels them naturally through the body’s regular processes.
Around 4 to 6 sessions of treatment are usually recommended for this modality. Since there is very little downtime involved, there is no need for an expensive and inconvenient hospital stay. Patients can take a short break from work during the lunch hour and attend a treatment session!
Post-treatment for Hori's Naevus
Some patients may notice visible lightening of pigmentation after the first laser treatment, although results vary depending on the type, depth and severity of the pigmentation. Further improvement may occur gradually over subsequent sessions as the skin responds to treatment.
Temporary redness or mild swelling may occur after treatment and generally subsides within a few hours to several days, depending on the laser technology and treatment intensity.
Post-treatment skincare typically includes gentle moisturising, appropriate skin barrier support and daily use of broad-spectrum sunscreen with SPF 30 or higher to help protect the treated skin and minimise further UV-induced pigmentation.