November 2019 | Case of the Month

The diagnosis is a comedo naevus. a rare hair follicle naevus first described in 1895. It is often linear and is characterised by a collection of black, keratin-filled follicles, which are not true comedones.

History

• Approximately 50% of lesions are evident at birth, with the other 50% developing during childhood, usually before the age of 10 years
• Inflammatory (acneiform) comedo naevi tend to arise during childhood or adolescence

Distribution

• A comedo naevus can affect any body site, although are most commonly found on the face, neck, trunk, and upper arm 

Morphology

• Closely grouped black keratinous plugs often distributed in a linear pattern, which is usually unilateral, and rarely bilateral. The affected patch may range in size from a few cm to a large area of skin
• Acneiform lesions can be associated with chronic inflammation and scarring

Management 

• Lesions are usually asymptomatic and safe to leave. However, treatment may be sought for cosmetic purposes
• Some improvement has been noted with topical retinoids, and also gentle hyfrecation of the individual comedones
• Acneiform lesions should be managed along the lines of acne. Troublesome cases not responding to appropriate topical / systemic treatment will need referring

For more information refer to the relevant chapter.