Becker nevus syndrome refers to a rare disorder comprising the typical pigmented lesion and its associated developmental abnormalities. Becker nevus itself is typically localized on the upper trunk, scapular or upper arm unilaterally; however, it can occasionally occur as multiple or bilateral lesions on any parts of the body. In this report, a rare case of multiple Becker nevi arranged in a unique checkerboard-like pattern is presented. More uniquely, the associated abnormalities found in this patient, breast hypoplasia and leg lipodystrophy, seem to be regionally correlated with the nevi. In closing, we would like to raise an easy-to-remember 6B’s mnemonic, which stands for Becker, Breast, Bone, Bowen’s disease, Basal cell carcinoma, and Beta-actin, for the cases of Becker nevus syndrome.
Becker nevus is a well-defined, irregular border, tan to dark brown hyperpigmented cutaneous hamartoma, which is commonly associated with hypertrichosis and presented in unilateral localized fashion on upper trunk. Less common sites are extremities, face/neck, abdomen, and lower back, respectively [
A 20-year-old woman presented with multiple hyperpigmented patches involving the entire right hemibody and left upper back since birth. The patches were asymptomatic and became darker during puberty. There was no family history of similar disorders. On skin examination, multiple well-defined, irregular-border hyperpigmented patches were observed on the entire right side of the body with alternate areas of pigmentary change and sharp demarcation at anterior midline, resembling a checkerboard mosaic pattern. Moreover, there were dark brown patches on left upper back extending towards left shoulder and left chest. Further examination showed left breast hypoplasia and a slight smaller circumference of right leg comparing to the left (Figure
Multiple Becker nevi on (1) anterior trunk resembling a checkerboard mosaic pattern, (2) left upper back extending toward left shoulder, and (3) the whole right leg. Slight smaller left breast and right leg circumference are seen.
On histopathology of the skin biopsy from left upper back and right abdomen, both sites exhibited acanthosis, slightly increased number of melanocytes along the basal layer of epidermis, mild elongation, and bridging of hyperpigmented rete ridges, compatible with Becker nevus.
Although most Becker nevi are found as isolated findings, some can be associated with abnormalities. Their precise etiopathogenesis still remains unclear. However, recent findings demonstrated that postzygotic lethal mutations in ACTB gene, a gene coding for beta-actin, may underlie the development of both Becker nevus and Becker nevus syndrome [
According to a systematic literature review by Schneider et al., there is a regional correspondence between the skin manifestation of Becker nevus and the malformation, providing a clue that there might be a common mutation during embryogenesis. Breast hypoplasia, maxillofacial dysplasia, and lipodystrophy were reported to have the strongest regional correspondence [
Checkerboard or flag-like or block-like pattern is one of the archetypical patterns, which is characterized by alternating squares with a sharp midline separation. It can be found in either cases of cutaneous mosaicism or genetic chimerism. In case of mosaicism, if the mutation occurred early in embryogenesis, it is more likely that abnormal clone will be widely spread, contributing to a larger number of skin lesions and multiorgan involvement [
The nature of Becker melanosis is benign; however, three reports have revealed that it might be associated with keratinocyte carcinomas such as basal cell carcinoma and Bowen disease. All of three cases developed cancerous lesions over the area of Becker nevus, which was a sun-protected and atypical site in a low-risk patient [
In conclusion, we present a case of Becker nevus syndrome which has very unique and interesting features. It is one of few cases that reveal a checkerboard mosaic pattern of Becker nevi and apparently point up the correlation between sites of Becker nevi and abnormalities involved. Moreover, we strengthen the point that long-term follow-up should be kept in mind for upcoming associated abnormalities, complication, and malignancy.
The authors declare that there are no conflicts of interest regarding the publication of this article.