The achromic naevus, a congenital white spot often confused with vitiligo.

It is not always easy to distinguish vitiligo from other pigmentation disorders. As a reminder, this skin disease is characterised by more or less extensive white patches on the skin. They are generally well-defined and are not scaly. Vitiligo macules are the result of the selective loss of melanocytes. These are the cells responsible for the synthesis of melanin, the pigment that gives skin its colour. Vitiligo is a multifactorial condition, involving autoimmune, genetic and external factors. It can be very difficult to live with due to its conspicuous and stigmatising nature, particularly in people with dark skin, where the patches of vitiligo are very visible.

Vitiligo is an acquired dermatosis, unlike the achromic naevus, which is an innate depigmentation.

The main distinction between vitiligo and achromic nevus is the age at which they occur. Although vitiligo can occur at any point in life, studies suggest that it predominantly develops before the age of 20. Conversely, an achromic naevus refers to a white spot present from birth. Moreover, unlike vitiligo, the achromic naevus is associated with a reduction in melanosomes, the organelles of melanocytes in which melanin is produced, rather than a destruction of melanocytes. The few melanosomes that manage to transfer into the keratinocytes during the process of melanogenesis are insufficient to pigment the skin uniformly, hence the emergence of a white spot.

Just like vitiligo, the achromic naevus presents itself in the form of well-defined white patches that can appear on any part of the body. Most often, it is a case of a single isolated spot, although this is not always the case. Another notable characteristic of the achromic naevus is its stability: the lesions do not spread and do not change in appearance over time, unlike those of the vitiligo. The diagnosis of these two conditions is done in the same way: clinically, with the aid of a Wood's lamp if necessary, a device that emits long UVA and violet light, allowing for the observation of the patches.

The management of vitiligo and achromic naevus is not quite the same. Capable of progressing and significantly affecting the quality of life, vitiligo generally needs to be treated. This often involves the topical application of immunosuppressants, such as tacrolimus, coupled with phototherapy. In case of failure of conventional treatments or segmental vitiligo, a melanocyte graft may be considered. The achromic naevus, not evolving over time, does not necessarily require treatment but, for aesthetic reasons, it is possible to resort to phototherapy or a skin graft.