A comedo naevus, also known as a naevus comedonicus, is an uncommon, benign cutaneous anomaly composed of clusters of dilated follicular openings that resemble comedones and contain soft, dark keratin.
Causes :
Although the specific source of nevus comedonicus is unknown, cutaneous mosaicism, or a cell line with a genetic defect, is thought to be the culprit. If this mistake happens early in the embryo development, the cells may spread out and result in many comedo naevi. A mosaic condition called comedo naevus is caused by somatic mutations during embryonic development. Increased expression of IL-1 alpha is thought to be correlated with FGFR2 mutations being significant.
Somatic NEK9 gene mutations have recently been reported. This results in the disruption of normal follicular differentiation and activation of NEK9 kinase. Although both follicular and non-follicular tissue has shown similar DNA alterations, a follicle-specific action of NEK9 has been proposed in the aetiology of comedo nevi.
Risks :
Adolescence is a common time for the problems, which include:
- Scarring
- infection with bacteria
- large cyst development
- persistent inflammation
Treatment :
Treatment for comedo naevus is frequently unneeded because it is benign and asymptomatic. For cosmetic purposes or to address problems like cysts and abscesses, treatment may be undertaken.
Oral treatments:
Although ineffective, antibiotics may be necessary to treat subsequent infections. Isotretinoin may reduce cyst formation, but long-term treatment is needed, thus it is not usually recommended.
Topical treatments:
Tretinoin and other topical retinoids +/- topical steroids or calcipotriol, acid salicylate . Use of lotions made of ammonium lactate.
