The red nail--always benign?

Red nail is a common disorder. However, a thorough examination of the patient's nails allows one to distinguish different diseases. For example, longitudinal erythronychia may be monodactylous or polydactylous. Only the former type can show histologically Bowen's disease or an amelanotic melanoma. Among the polydactylous type, the nosologic position of the acantholytic and dyskeratotic naevus versus Darier's disease is still controversial. Acantholytic epidermolysis bullosa looks like bullous Darier's disease, and acrokeratosis of Hopf may present also red longitudinal streaks. Subungual warty dyskeratoma is rare, but other dermatoses such as lichen planus, psoriasis, mail melanoma and various tumours have to be ruled out. Finally nail involvement in amyloidosis may precede the other signs of this systemic disease. The purpose of this paper will be focused on red nails that can present principally with red lunulae, solitary longitudinal erythronychia and multiple longitudinal erythronychia. Other aspects of this feature will also be raised.