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No pigmented moles

Amelanotic nevus (Amelanotic nevus): This disease occurs when the baby is born or shortly after birth, and it expands proportionally with age. The damage is often distributed along the nerve segment. It is manifested as localized or generalized reduction of stains, and the rash has a very edge Irregular, no pigmentation, not as obvious as vitiligo. Sometimes the leukoplakia is mixed with light brown miliary grains to lentil freckle-like spots, and it feels normal. If the surrounding skin is pressed to make it ischemic, the boundary between the affected part and the surrounding skin still exists. The skin lesions remain unchanged for life, which is one of the types of nerve nevi.

Vitiligo and non-pigmented moles

Non-pigmented moles, also known as bleached moles, are a common mole. The incidence of newborns is about 1/125.

【Cause and Pathology】

It may be caused by somatic mutations in early embryonic development.

【Clinical manifestations】

Vitiligo is present at birth and can occur in any part of the body, but it is most common in the trunk. It is often distributed on one side. It can be round or square in size from 0.5 to 10 cm. A few cases have a segmental or systemic distribution.

【Histopathology】

The number of melanocytes in the lesion is normal or decreased, dendrites are dysplasia, and melaninized melanosomes are normal in size, but the number is decreased. Melanocytes contain autophagosomes. Melanosomes gather into bundles.

【Key Points of Identification】

1. Vitiligo is an acquired disease, which has a late onset, while non-pigmented moles have an earlier onset.

2. Vitiligo has a clear border, with deepening of the pigment on the border, but no pigmented mole, the border is not obvious, and there is no deepening of the pigment. Vitiligo persists for life.

3. Vitiligo melanocytes are reduced or disappeared, non-pigmented moles are more normal, the number of melanosomes is reduced, it contains autophagosomes, and melanosomes gather into bundles.

Type

Non-pigmented moles can be divided into three types according to the distribution of skin lesions.

①Isolated type: single leukoplakia, round or oval.

②Segmental type: skin lesions are distributed according to skin segments, involving one or more skin segments, or distributed along the Blaschko line.

③Systemic type: leukoplakia involving the entire unilateral limb. The shape of the leukoplakia is strange, swirling and streaking, similar to splashing white paint.

Pathological changes

a The number of melanocytes in the basal layer is normal, but the Dopa response is weakened.

b Silver staining shows the reduction of melanin particles in the epidermis,

c Ultrastructure: Melanocytes shrink, dendrites decrease, and the number of melanosomes is normal or decreased.