Yellowish-brown spotty pigmentation on the facial skin, which is autosomal dominant. Sun exposure can induce and aggravate the lesions. The number of melanocytes in the epidermis does not increase in freckles, but the number of melanosomes increases significantly and is rod-shaped.
I. Overview
It is an autosomal dominant pigmentation spot on the facial skin. Sun exposure can induce and aggravate the lesions.
Etiology
Genetic predisposition, autosomal dominant inheritance. Sun exposure is a necessary factor for the development of the rash.
Clinical manifestations
Most lesions appear around the age of 3-5 years, more often in females. The number increases gradually with age. The rash occurs on the face, especially the nose and cheeks, and can involve the neck, shoulders, back of the hands and other exposed areas, but no rash on non-exposed areas. The lesions are light brown or dark brown pinhead-sized to green bean-sized rashes, round, oval or irregular. They are scattered or clustered and do not fuse in isolation. No conscious symptoms. The rash deepens in color and increases in number after sun exposure in summer, but decreases or disappears in winter. There is often a family history.
Examination
Pigmented spots are dotted or round, ovoid, or in various irregular shapes, distributed on the face, especially around the nose and cheeks, the size is as large as a needle point to a grain of rice, the diameter is generally less than 2 mm, light brown to dark brown, the number of distribution is a few dozens, more than a hundred, most of them are densely distributed, but do not fuse with each other, isolated around the face, serious cases can also be seen on the back of the hands, neck, front and back of the ears, ear cavity, shoulder In severe cases, they can also be seen on the back of the hands, neck, front and back of the ear, ear cavity, shoulder and arm and other exposed parts of the body, mostly symmetrically.
Histopathology: there is an increase in melanin in the epidermis, but not in melanocytes, and electron microscopy shows that the melanocytes there are significantly different from those in the adjacent normal skin, showing larger and stronger dopa-positive reactions, with more and longer dendrites and melanosomes in the form of long rods.
V. Diagnosis
The number of melanocytes in the epidermis at the freckles does not increase, but the number of melanosomes increases significantly and is rod-shaped.
Differential diagnosis
It should be distinguished from freckle-like nevus, nigra and light staining dry skin disease.
VII. Treatment
1.Depigmentation treatment.
3%-5% hydroquinone cream, 0.1% vincristine ointment, 3%-5% arbutin cream, 20% azelaic acid cream, 1% tretinoin cream, etc. Adhering to external application for several months can have certain effect.
2, corrosion, destructive treatment.
In the past, liquid nitrogen freezing, trichloroacetic acid or phenol dabbing, mechanical grinding, high-frequency electricity, ordinary CO2 laser and other treatments can make freckles peel off, but the above treatments are not selective to the lesions and often cause some sequelae, which need to be operated carefully, and the treatment is too deep and easy to cause depressed scar or hyperplastic scar, and may lead to pigmentation or hypopigmentation, at the same time, the treatment process is painful and difficult for patients to accept.
3.Laser selective treatment.
Modern Q-switched laser has a high degree of selectivity in the treatment of freckles, which is the best method for treating freckles at present.
VIII. Prognosis
You should try to avoid or reduce the hot sun exposure, or apply sunscreen-type light-avoidance agent to reduce the occurrence of freckles or the deepening of freckle color.