What causes a comedo naevus?
The comedo naevus is thought to be due to a mosaic genetic abnormality, i.e. a line of cells with a genetic error. If this error occurs early in development of the embryo, the cells may spread out to cause multiple comedo naevi. Mutations in FGFR2 have been detected in the naevi of some patients. This is the same gene that has found to be abnormal in a more serious generalised genetic condition, Apert’s syndrome so the comedo naevus may be a ‘mosaic’ of Apert’s syndrome (some cells have the abnormal gene, and other cells have the normal gene). Apert syndrome causes craniofacial dysostosis (abnormalities of the bone structure of skull and face) and other skeletal abnormalities. Patients with Apert’s syndrome often suffer from severe acne, which also arises within a comedo naevus.
