Nail Disorders and Abnormalities

oPatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

Nail abnormalities are common. Appearances may be difficult to diagnose with certainty and care must be taken to ensure correct diagnosis and therefore treatment.

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  • Ingrowing toenail:
    • Common problem resulting from various causes, eg improperly trimmed nails, hyperhidrosis, and poorly fitting shoes.
    • Often presents with pain, but may progress to infection and difficulty with walking.
    • Treatment options include cutting nails square, hot water soaks, antibiotics for excision, and wedge excision or total excision of nail.
  • Beau's lines:
    • Transverse ridges are usually transient and due to a temporary disturbance of nail growth, eg severe illness.
  • Green nails:
    • Caused by pseudomonal infection.
  • Blue nails:
    • May occur as a side effect of anti-malarial drugs.
  • Black nails:
    • May be a feature of Peutz-Jeghers disease, vitamin B12 deficiency and post-irradiation.
    • Black streaks may indicate a junctional melanocytic naevus or malignant melanoma.
  • Leukonychia (white nail):
    • May be congenital or due to minor trauma, hypoalbuminaemia in chronic liver disease, renal failure, fungal infection or lymphoma.
  • Yellow nail syndrome:
    • Slow growing, excessively curved and thickened yellow nails which are associated with peripheral lymphoedema and exudative pleural effusions.
  • Clubbing (an increase in the soft tissue of the distal part of the fingers or toes); common causes of finger clubbing include:
  • Koilonychia
    • Dystrophy of the fingernails in which they are thinned and concave with raised edges (spoon shaped nails).
    • May be due to iron deficiency or trauma.
  • Nail-patellar syndrome:
    • Congenital nail disorder, autosomal dominant inheritance.
    • The patellae and some of the nails are rudimentary or absent.
  • Longitudinal ridging:
  • Nail becomes detached from its bed at base and side, creating a space under nail that accumulates dirt. Air under nail may cause grey-white colour but can vary from yellow to brown.
  • In psoriasis can see yellowish-brown margin between margin between normal nail (pink) and detached parts (white).
  • If Pseudomonas aeruginosa grows underneath nail, then green colour.
  • When nail bed separation begins in middle of nail then appearance resembles an 'oil spot' or 'salmon-patch'.
  • Causes of onycholysis include:
    • Idiopathic or inherited
    • Systemic disease, eg thyrotoxicosis
    • Skin disease, eg psoriasis
    • Local causes, eg trauma or chemicals
  • Thickening of nail plate mainly seen on big toes of elderly associated with injury to foot, badly fitting shoes or poor blood supply.
  • Central grooves in centre of nail. Also cuticle is pushed back and inflamed.
  • Most commonly results from compulsive habit of patient picking at proximal nail fold thumb with index fingernail.
  • Disappears if patient stops the habit.
  • Virtually all patients with psoriasis have nail involvement at some time and occurs in 50% of cases at any given time.
  • Abnormalities include nail pits, transverse furrows, crumbling nail plate, roughened nails.


  • Nail pitting is associated with alopecia areata as well as with psoriasis.
  • Can sometimes see in nail bed 'oil spot', distal onycholysis, distal subungual hyperkeratosis, splinter haemorrhages and false nail following spontaneous separation of nail plate.
  • Nails involved in approximately 10% of cases of disseminated lichen planus. However, may be only presentation of disease.
  • With matrix causes thinning, brittleness, crumbling of the nail with accentuated surface longitudinal ridging and colour change to black or white.
  • Typically the lunula is raised more than the distal part of the nail.
  • Severe chronic inflammation causes either partial or complete loss of nail plate and formation of pterygium (see picture below) with partial loss of central nail plate seen as distal notch or completely split nail. Involvement of nail bed causes onycholysis, distal subungual hyperkeratosis, formation of bulla or permanent anonychia.


  • Lichen planus can affect any number of nails.
  • Treatment: injection of steroid into proximal nail fold.
  • Squamous cell carcinoma:
    • Usually caused by infection with human papillomavirus types 16 and 18.
    • Skin-coloured or hyperpigmented lesions appearing as keratotic or hyperkeratotic or warty papules and plaques found on the proximal and lateral nail folds and hyponychium.
    • Squamous cell carcinoma in situ (SCCIS) can extend into the nail bed producing onycholysis.
    • Invasive SCC arising within SCCIS can cause pain if invades bone.
    • Occurs much more commonly on fingers, usually thumb and index finger usually as solitary lesion.
    • Can involve multiple fingers in immunocompromised patients.
    • Treat with CO2 laser ablation, Mohs' surgery or amputation of digit if necessary.
  • Nail matrix nevomelanocytic nevus:
    • Presents as a longitudinal brown strip in the nail bed.
  • Acrolentiginous melanoma:
    • Mostly seen in thumb and big toe with brown-black pigmentation of nail extending to proximal and lateral nail folds and even beyond the nail (Hutchinson's sign), usually without other symptoms.
    • Mean age of patients is 55-60 years.
    • Cause of 2-3% of melanomas in white patients and 1 in 5 or 6 black patients.
    • Diagnosis is by biopsy. 5 years survival is 35-50%.

See separate article - Fungal Nail Infections.

Paronychia is inflammation of the tissue around the finger nail, with pus accumulating between the cuticle and the nail matrix. The area may become swollen, red and tender. Acute paronychia is usually due to bacterial infection, particularly Staphylococcus aureus. Chronic paronychia may be associated with eczema or psoriasis. It is often due to candidal infection but other pathogens, eg Pseudomonas spp. (produces a green or black discolouration) may be the cause.

  • Acute paronychia:
    • Erythema, swelling and throbbing pain in the nail fold caused by bacterial infection, eg S. aureus and Group A streptococci.
  • Chronic paronychia:
    • Commonly occurs in patients whose hands are constantly in water with repeated minor trauma damaging the cuticle so that irritants can further damage the nail fold.
    • Proximal and lateral nail folds show erythema and oedema with loss of cuticle and part of proximal nail fold separating from nail plate.
    • Commonly becomes infected especially with C. albicans. Eventually nail fold retracts becomes thickened and rounded.
    • There are episodes of painful acute inflammation often due to infection between the proximal nail fold and nail plate from which pus may drain.
    • Over time, lateral edges of nail plate become irregular and discoloured and eventually entire nail plate becomes involved showing numerous transverse grooves.
    • Treatment is to remove source of irritation, topical steroids and weekly doses of fluconazole.[1]

Further reading & references

  1. Tosti A, Piraccini BM, Ghetti E, et al; Topical steroids versus systemic antifungals in the treatment of chronic paronychia: an open, randomized double-blind and double dummy study.; J Am Acad Dermatol. 2002 Jul;47(1):73-6.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Dr Colin Tidy
Current Version:
Last Checked:
Document ID:
1096 (v23)