Leukoderma and Vitiligo: Are there differences between these conditions?

Leucoderma is a term derived from the ancient Greek leukós, meaning white, and dérma, referring to the skin. The etymology of this term allows us to understand that it is related to a white discoloration of the skin. According to the dictionary of the National Academy of Pharmacy, leucoderma is defined as follows: "Hypopigmentation or depigmentation of areas of the epidermis due to a deficiency or absence of melanin. It can be congenital, as in albinism, or acquired, for example in leprosy, psoriasis, syphilis, vitiligo or the scar tissue of a wound."

Vitiligo is a specific form of leukoderma characterized by a selective loss of melanocytes.

There are several types of leukoderma, which can result from various causes. Leukoderma can thus be the consequence of a lack of melanin pigment, due to a decrease in the number of melanocytes or a defect in the synthesis or transfer of melanin, localized vasoconstriction, a deposit of white substance such as cutaneous calcification for example, tension exerted on the epidermis, by a cyst wall notably, a skin infarction such as in white atrophy or Degos disease or even a keratosis as in warts or molluscum contagiosum. Leukodermas can be diffuse or circumscribed. Based on this criterion and the age at which they appear, it is possible to differentiate them and determine if it is a case of vitiligo, as shown by the decision tree below.

Vitiligo results from a decrease in the number of melanocytes, leading to white patches, which are typically round and well-defined. Multiple mechanisms can contribute to the loss of melanocytes, including metabolic abnormalities, oxidative stress, cell detachment, inflammation, autoimmunity, and more. The contribution of each of these factors is not yet clear, but it appears that an intrinsic defect in the melanocytes is the initial event, and that maladaptation to oxidative stress in the melanocytes leads to a local inflammatory response and the activation of innate immunity. This skin discoloration mechanism is specific to vitiligo and varies among leukodermas.

Key point to remember : All cases of vitiligo are instances of leukoderma, but not all cases of leukoderma are vitiligo.

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