This page outlines the terms used by dermatologists to describe diseases of the fingernails and toenails.
Nail plate abnormalities are often due to inflammatory conditions affecting the matrix or nail bed. Specific diagnoses may be made from characteristic appearances.
Beau line is a transverse depression affecting all nails, due to acute systemic illness stopping nail growth.
Median canaliform nail dystrophy
This form of median nail dystrophy presents as a feathered, central, longitudinal ridge. Sometimes it is due to repetitively pushing back the cuticle (habit-tic deformity). Macrolunulae (large half-moons) may expose the nail to trauma, as they are frequently present.
Onychogryphosis is a thick hard curved nail plate in the shape of a ram's horn.
due to ageing, psoriasis or trauma.
Angel-wing deformity describes nail plate thinning due to lichen planus.
Nail plate crumbling
Onychoschizia is distal lamellar or splitting/brittle nails due to water/detergent damage.
Longitudinal splitting is an extension of ridging seen in psoriasis, fungal nail infection or lichen planus. Distal splitting in association with a pigmented or red linear band can be a sign of onychopapilloma.
Trachyonychia is characteristic of lichen planus.
These images show acrylic nails used as decorative cosmetics.
Distinguish a discoloured nail bed from a discoloured nail plate.
Yellow nail syndrome
Yellow nail syndrome refers to yellow or green nails due to lymphatic obstruction in cardiopulmonary disease.
Lateral yellow streak
Yellow nails due to psoriasis
Oil drop or salmon patch
White nails. Consider hypoalbuminaemia or chronic renal failure. May be familial. Transverse leukonychia, in which there are multiple parallel white lines, is thought to be due to manicuring. It may also arise in association with Beau lines.
These images show white streaks due to trauma, eg manicuring.
These images show lifting of the distal nail plate, which appears white or yellow. Consider idiopathic causes, trauma, psoriasis, thyrotoxicosis, irritant and allergic contact dermatitis, fungal nail infection (candida), drug photosensitivity (especially tetracycline and psoralens)
Superficial white onychomycosis
Half-and-half nails are seen in renal failure. White proximal nail, with brown distal nail.
Terry nail is seen in liver cirrhosis. White proximal nail, reddened distal nail.
Mee lines are partial leukonychia due to arsenic intoxication or systemic disease.
Muehrcke lines are a double band of leukonychia in renal disease.
Red longitudinal streaks
A red longitudinal streak or erythronychia is often due to onychopapilloma.
Red and white streaks
See Darier disease.
Red tender area
If a red spot is tender, consider glomus tumour.
If nails are discoloured blue, consider drugs if all nails are affected, in this case due to minocycline.
A red or purple streak is known as a splinter haemorrhage.
Subungual haemorrohage or haematoma (blood clot) causes a purple or black discolouration.
A black nail may be due to pseudomonas infection
Multiple brown linear streaks
Expanding variable colour/shaped streak
The cuticle is an area of keratin joining the skin of the posterior nail fold to the nail plate. Loss of cuticle results in paronychia.
Ragged cuticles are characteristic of connective tissue disease, and also occur in parakeratosis pustulosa.
Hang nail is due to trauma (biting).
Nail fold telangiectases
Nail fold telangiectases are characteristic of connective tissue disease, eg lupus erythematosus.
Staphylococcus aureus is the main cause of acute paronychia.
Herpes simplex is another common cause of acute paronychia.
Acrodermatitis continua of Hallopeau
Retronychia refers to embedding of the nail into the nail fold and subsequent inflammation.
Clubbing is due to hypertrophic osteoarthropathy or thryoid disease (acropachy); see hypertrophic osteoarthropathy.
Koilonychia is a thin, spoon-shaped nail, and can be seen in normal children and adults. It is also associated with iron deficiency anaemia, diabetes, protein deficiency, connective tissue disease, nail exposure to solvents and and acitretin treatment.
Pincer nail is sometimes familial or associated with psoriasis.
Usually traumatic eg nail biting; in children parakeratosis pustulosa
Common skin lesions around nails include: