Becker nevus syndrome is characterized by the presence of a particular type of organoid epithelial nevus showing hyperpigmentation, increased hairiness and hamartomatous augmentation of smooth muscle fibers, in association with other developmental defects such as ipsilateral hypoplasia of breast and skeletal anomalies including scoliosis, spina bifida occulta, or ipsilateral hypoplasia of a limb. Usually, but not invariably, all of these anomalies involve the same side of the body as the nevus. Because the nevus is androgen-dependent anomaly, the "full-blown" picture of Becker nevus is in general observed exclusively in adolescent or adult men. In women and prepubertal boys the lesion is much less conspicuous because the pigmentation is less intense and hairiness is absent or only mild. The male to female ratio of cases of Becker nevus syndrome so far reported is approximately 1:2. This is explained by the fact that unilateral hypoplasia of breast is an easily recognizable anomaly; therefore, it is more reported. Thus, it is suggested that with more thorough clinical studies the true ratio would probably be 1:1.
Ibrahim et al. (1995) reported a 17-year-old female with Becker nevus syndrome. She had an asymptomatic, gradually progressive, brownish lesion of one year duration on the right shoulder, right arm and adjoining part of right side of the chest. The onset was insidious. None of the other family members were said to have similar lesion. Examination revealed a well defined, irregular, smooth, non-scaly, uniformly brownish patchy lesion in geographical configuration. Hypertrichosis was not found to be hypoplastic. The texture of the lesional skin was normal. On systemic examination, no abnormality was detected.
[Ibrahim K, Tallab T, Bahamdan KA, Khare AK. Becker's Nevus and Ipsilateral Breast Hypoplasia. Gulf J Dermatol. 1995; 2(2):43-4.]