Becker\'s nevus (BN) is a kind of epidermal cutaneous hamartoma. A noticeable hyperpigmented patch with a big, unilateral, hyperpigmented macule and irregularly shaped borders is the manner in which BN often presents. In this case, a 16-year-old boy has asymptomatic dark brown colored follicular macule on the left side of the cheek shortly after birth. The lesions were initially inconspicuous but gradually became darker as time passed. The macules on some of them grew hair. This case of BN with apparent hypertrichosis on one side of the cheek, which made it challenging to make a differential diagnosis with whiskers. The primary point of differentiation is that the lesions of BN only appear unilaterally. On the other hand, the face has whiskers on both sides. Additionally, BN will show hyperpigmentation whereas whiskers do not. In conclusion, for its unusual clinical presentation, we believe that reporting this case may help dermatologists avoid misdiagnosing similar cases.

Becker\'s nevus (BN) is a cutaneous hamartoma which is characterized by circumscribed hyperpigmentation with hypertrichosis. Recent studies have revealed that BN patients harbored postzygotic ACTB mutations, which were restricted to arrector pili muscle lineage. We screened for ACTB mutations in 20 Chinese patients with BN and found that recurrent mutations (c.C439A or c.C439T) in ACTB were detected in the majority of BN patients. However, more than 20% of the patients were negative for ACTB mutations, suggesting a possible genetic heterogeneity in Becker\'s nevus. Interestingly, these mutations were also detected in dermal tissues outside the arrector pili muscle. We further performed genotype-phenotype correlation analysis, which revealed that lesions above the waistline, including the trunk above the anterior superior spine level, upper limbs and face, or covering more than 1% BSA were more likely to be positive for ACTB mutations. Altogether, our results provide further evidence of postzygotic ACTB mutations in BN patients and suggest a possible genotype-phenotype correlation of BN.

Becker\'s nevus is a common pigmented dermatosis, usually featured by ipsilateral pigmented patch with hypertrichosis. Becker\'s nevus is often treated with various types of lasers although other regimens are available. However, clinical outcomes appear inconsistent among studies. To summarize the clinical outcomes of Becker\'s nevus treated with lasers via literature review. A variety of lasers had been used alone or in combination to treat Becker\'s nevus. Laser wavelengths used for Becker\'s nevus ranged from 504 to 10,600 nm, while the number of treatment varied from 1 to 12 sessions. The clinical outcomes were mixed although combination of lasers with different wavelengths appeared to achieve a better efficacy. Adverse effects were usually mild to moderate erythema. While lasers are relatively safe, their efficacy for Becker\'s nevus is moderate. It seems that combination therapy could improve the outcome. However, trials in larger group of patients are required to validate the efficacy of each type of lasers for Becker\'s nevus.