Nevus of Ota, a pigmented birthmark characterized by a cyanotic nevus in the periocular region, common in Eastern peoples (although sometimes not always present at birth), was first described formally and systematically by Ota in 1938 and is essentially a disease of increased melanin in the dermis that often coincides with the distribution of the branches around the trigeminal nerve. Nevus of Ota is a common disease in Mongolian East Asia, and in Japan, patients with nevus of Ota account for about 0.4% of dermatology visits and 2.6% of plastic surgery visits, with a male-to-female ratio of 1:3. About half of the patients are found to have the disease at birth, but it is also found in childhood, and some patients do not show it until adolescence, manifesting as patches of brown, gray, and blue spots with indistinct borders. The lesions have unclear borders, and the color of the spots can be monochromatic or a combination of these colors, and the shades vary. Due to the different density and location of melanocyte distribution in the dermis, the patches can be light brown to dark blue, and different parts of the same lesion can have different colors. In some patients, the lesions have the tendency to increase slowly. The patches occur in the forehead, around the eyes, cheeks and zygomatic area, i.e., the area equivalent to the distribution area of area I and II of the trigeminal nerve, which may occupy all or part of the area. Some patients start to grow slowly in early stage, but the self-limitation of growth is difficult to be determined. Some patients start to be stable in long term when they are children, and most of them think it will be more stable after puberty, but some others still have the tendency to grow slowly until they are about 30 years old. Nevus of Ota has no hereditary tendency, and there is no clear relationship with malignant transformation. The treatment of nevus of Ota is cosmetically oriented, and its principle should be to remove the pigment of the lesion without leaving scar and without causing pigmentation or loss. In the past, various treatments, such as dry ice compression, liquid nitrogen freezing, skin grinding, skin implantation, skin peeling, C02 laser treatment and even radionuclide treatment, can reduce the pigment of skin lesions, but it is difficult to get a complete cure, and it is easy to cause scarring or pigment loss, and the treatment process is painful and the efficacy is extremely unsatisfactory.
The new laser selects the laser wavelength as the peak absorption of melanin, and adopts Q modulation technology to obtain great instantaneous power and very small pulse width, acting on the melanin vesicles in melanocytes and causing melanocytes to break up. The broken cells and melanin, etc. are engulfed by phagocytic cells and transported through the lymphatic system and finally discharged through the kidneys. Due to the extremely pure wavelength of the laser, the normal tissue without melanin absorbs very little, and the extremely short pulse width ensures that the surrounding normal tissue is not damaged. At present, the commonly used lasers mainly include 755nm emerald laser, 1064nm Nd:YAG laser, 694nm ruby laser, etc. These lasers all adopt Q modulation technology. Before treatment of nevus of Ota, clean the face, apply EMLA local anesthetic cream locally for 30min-lh, disinfect with benzalkonium bromide (Neosporin), and then use the laser to irradiate the lesions evenly. After treatment, the lesion area will be grayish white immediately and then gradually dark red petechiae will appear.