Exogenous white stains and particularly superficial white onychomycosis (Jessner’s leukonychia trichophytica) cause white nails. In temperate climates the cause of superficial white onychomycosis is usually Trichophyton mentagrophytes, but in hot and humid climates also moulds such as Fusarium species may infect the surface of the nail plate. The nail is white and opaque also in [...]
All conditions leading to onycholysis also cause apparent leukonychia. Psoriasis may cause both true and apparent leukonychia. True leukonychia is due to matrix involvement, and apparent leukonychia to onycholysis and/or parakeratosis of the nail bed. One of the earliest signs of leprosy is apparent macrolunula, which may become total in dystrophic leprosy. Table 7.1 Causes [...]
Isolated longitudinal leukonychia is an example of localized metaplasia. It is characterized by a permanent, greyish-white longitudinal streak, 1 mm wide, below the nail plate. Histologically there is a mound of horny cells causing the white discoloration due to a lack of transparency, leading to alteration in light diffraction. Subungual filamentous tumour is the most [...]
Punctate leukonychia is characterized by white spots 1–3 mm in diameter occurring singly or in groups almost exclusively on finger nails. They are usually due to repeated minor trauma to the matrix. The evolution of the spots is variable; appearing generally on contact with the cuticle, they grow distally with the nail. Approximately half of [...]
In subtotal leukonychia there is a pink arc of about 2–4 mm in width distal to the white area. Nucleated cells in the distal area were believed to mature, lose their keratohyalin granules and then produce normal nail keratin several months after their formation. It was also suggested that parakeratotic cells are present along the [...]
The clinical and histological features of the skin changes in Reiter’s syndrome may be indistinguishable from those of psoriasis. Skin changes resembling paronychia can accompany nail involvement suggesting inflammation of the proximal nail fold. Onycholysis, ridging, splitting, greenish-yellow or sometimes brownish-red discoloration and subungual hyperkeratosis may be present. Small yellow pustules may develop and slowly [...]