It is easy to identify a localized hypopigmented area in a dark-skinned individual. It can however be a difficult task to identify a widespread hypopigmentation in a fair skin individual. The extent of the reduction in pigmentation can be evaluated comparatively with the surrounding healthy skin if it is a localized hypopigmentation, whereas when the whole integument is involved, evaluation is done by comparing with the parents’ skin color. In some cases, when the lesions are widespread, it can be difficult to determine whether it is primary a disorder of hyper- or of hypopigmentation. Hence history taking, the effect of tanning, and the inspection of naturally less pigmented areas such as inner arms and buttocks can be helpful. In other areas, lesions may instead be very subtle. Wood’s lamp examination may then assist the identification of leukodermas that are due to reduced epidermal melanin content, by enhancing the contrast with normally pigmented skin.

Important clues in establishing diagnosis of a leukoderma are its diffuse or circumscribed nature as well as the age of lesion onset. It is therefore convenient to distinguish between (at least initially) circumscribed leukodermas and diffuse leukodermas: the latter affecting the entire integument, as well as the appendages, and corresponding mainly to the various types of albinism (cf. algorithm, Table 16.1). Other elements essential to the establishment of differential diagnosis are the age of lesion onset, the presence of lesional hyposensitivity (leprosy), family background, and other related signs. Certain particular clinical aspects such as confetti-like or guttate leukodermas (Box 16.1), or blaschkolinear leukodermas (Box 16.2), also help to guide the diagnosis. Lastly, it is essential to specify whether the lesion was straightaway leukodermic or not. When the hypopigmented area was preceded by another lesion, the diagnosis of a postinflammatory hypopigmentation or a regressing tumor is plausible.