Localised white skin lesions also signify a limited number of diseases. Working down, on the face consider pityriasis alba, a low grade form of eczema, poliosis, a white area on the forehead with a tuft of white hais from birth. If poliosis appears as a new lesion consider localised vitiligo. White spots on the chest or arms with fine surface scale is pityriasis versicolor. White spots on the forearms or lower legs are idiopathic guttate melanosis, a type of inverse freckle from sun damage. Porcelain white spots on the trunk with surface skin wrinkling is due to lichen sclerosus/ morphoea.
White patches present at birth should raise the possibility of tuberous sclerosus.
Hypopigmentation on the trunk includes that on the chest, back and abdomen.
The commonest conditions causing hypopigmentation at these sites include vitiligo, Halo nevi, Pityriasis versicolor and post inflammatory either after liquid nitrogen or surgery to skin cancers. Post inflammatory hypopigmentation is also seen with discoid lupus erythematosus. Localised morphea or lichen sclerosus can also present as hypopigmented patches but the underlying skin will be firm in morphea. Undertreated psoriasis or eczema of the trunk may also present as hypopigmented patches but some evidence of these conditions elsewhere should allow you to make the diagnosis.
In the newborn look for the ashleaf macules of Tuberous sclerosus or pale connective tissue nevi. Segmental vitiligo may also be seen congenitally. Nevus depigmentosus and nevus anaemicus may also present as hypopigmented patches in this age group.
