A 16-year-old boy presented with a hyperpigmented patch over his left chest since puberty
Dr. Adrian KC Cheng

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Clinical history:

A 16-year-old boy presented with a hyperpigmented patch over his left chest since puberty. Examination showed a brownish patch to thin plaque with irregular borders and mild hypertrichosis over his left upper chest. There were also a few superimposed acneiform papules. Dermoscopy showed a well-defined pigment network with uniform thickness of lines and perifollicular hypopigmentation.

What is the diagnosis?

Answer:
A. Becker melanosis

Becker melanosis typically presents during adolescence, often around puberty, as a unilateral, irregularly bordered hyperpigmented patch or thin plaque on the upper trunk, chest, or shoulder. The presence of mild hypertrichosis and superimposed acneiform papules further supports the diagnosis, as Becker melanosis is androgen-sensitive and frequently shows increased hair growth and acneiform changes within the lesion. Becker melanosis is a benign cutaneous hamartoma involving epidermal melanocytes, hair follicles, and dermal smooth muscle. It shows a strong male predominance and usually appears around puberty due to increased androgen receptor expression within the lesion. The condition may be isolated or associated with developmental anomalies in Becker nevus syndrome, including ipsilateral breast hypoplasia, skeletal deformities, or muscular abnormalities. The condition is benign and non-progressive, and treatment is usually for cosmetic reasons only. Laser therapies targeting pigmentation and hair growth may offer partial improvement, though responses are variable. Routine surveillance is generally not required.

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The slide and the question were prepared by:

Dr. Adrian KC Cheng, ^{MBBS(HK), MRCP(UK), MSc GEOR (CUHK), FHKCP, FHKAM (Medicine)}

Specialist in Dermatology & Venereology;

Associate Consultant,

Division of Dermatology, Department of Medicine, Queen Mary Hospital, Hong Kong SAR