[Becker nevus syndrome].

Becker nevus is a hyperpigmented hamartoma with an irregular outline and often hairy. It is normally found on the shoulders and chest, although it can appear in other areas. Becker nevus is sometimes associated with other muscular, skeletal, or cutaneous abnormalities such as ipsilateral breast hypoplasia or scoliosis. This characteristic phenotype of Becker nevus associated with unilateral breast hypoplasia or other abnormalities is referred to as Becker nevus syndrome. Although the lesions usually become apparent during adolescence, they are present from birth and represent part of the spectrum of so-called epidermal nevus syndromes. We present 4 cases of Becker nevus syndrome in which Becker nevus was associated with ipsilateral breast hypoplasia and, less consistently, other abnormalities.