Photo Rounds

Unusual patch of skin

A 15-year-old boy presented to his family physician (FP) with an unusual patch of skin on his right chest. His mother said that the patch was present at birth, but it had become more noticeable over the past year. The boy was getting acne on his face, and his mother wondered whether the patch was related to that. The boy was otherwise in good health.

What’s your diagnosis?


The physician diagnosed nevus comedonicus on the chest of this 15-year-old boy.

This is a congenital hamartoma with open comedones; it is not acne. Nevus comedonicus (comedonal nevus) is a rare congenital hamartoma characterized by an aggregation of comedones in one region of the skin. Comedonal nevi do not become melanoma because they lack melanocytes. Therefore, there is no reason to excise them other than for cosmetic reasons. However, comedonal nevi are large and the risks of excision outweigh the benefits.

In this case, the patient and his mother were reassured that no treatment was needed and they opted to leave it alone.

Photos and text for Photo Rounds Friday courtesy of Richard P. Usatine, MD. This case was adapted from: Smith M, Usatine R. Benign nevi. In: Usatine R, Smith M, Mayeaux EJ, et al. Color Atlas of Family Medicine . 2nd ed. New York, NY: McGraw-Hill; 2013:945-952.

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