Nail Disorders & Abnormalities

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

Some Common Nail Disorders

  • Ingrowing toenail:
    • Common problem resulting from various causes, e.g. improperly trimmed nails, hyperhidrosis, and poorly fitting shoes.
    • Often presents with pain, but may progress to infection and difficulty with walking.
    • Treatment: See Ingrown nails in treatment menu.
  • Beau's lines:
    • Transverse ridges are usually transient and due to a temporary disturbance of nail growth, e.g. Illness, stress.
  • Green nails:
  • Blue nails:
    • May occur as a side effect of anti-malarial drugs
  • Black nails:
  • Leuconychia (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
  • Koilonychia
    • Dystrophy of the nails 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, e.g. thyrotoxicosis
    • Skin disease, e.g. psoriasis
    • Local causes, e.g. 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 longitudinal grooves dystrophy

  • 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 habit

Splinter haemorrhages


  • 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.

Lichen planus

  • 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.

Fungal Nail Infections - Onychomycosis

See separate article - Fungal Nail Infections.

  • Distal and lateral subungual onychomycosis (DLSO)
    • Is the commonest form and is virtually always caused by dermatophytes.
    • Infection starts under front of nail or nail fold and extends under the nail to involve the whole structure. Can either affect a healthy nail or one already diseased, e.g. by psoriasis.
    • Approximately 80% of cases occur on the feet, especially on big toes often affecting both toe and fingernails.
    • Initially presents as white patch on the under surface of the nail and nail bed but becomes discoloured to brown or black.
    • Progression can incur within weeks or more slowly over months or years with the nail becoming opaque, thickened and cracked, friable and raised from the nail bed.
  • Superficial white onychomycosis (SWO)
    • Usually caused by dermatophyte invading surface of dorsal nail plate presenting as white chalky plaque on proximal nail plate almost exclusively on the toenails.
    • Nail plate may become eroded and even lost.
  • Proximal subungual onychomycosis
    • Almost always associated with immunocompromised patients presenting as a white spot beneath the proximal nail fold which eventually fills the lunula occurring most commonly on toenails.
    • Eventually can involve whole of the under surface of the nail plate.
  • Candida onychomycosis: occurs in 3 different types:
    • Candida paronychia: initially appears as oedema, erythema and pain of the nail fold from which pus can be expressed at times. Also nail plate becomes dystrophic with patches of opacification or discolouration (white, yellow, green or black) with transverse furrows. Usually, pressure on the nail causes pain. Most cases are on fingernails usually middle finger.
    • Subungual abscess with DLSO occurring in the setting of onycholysis (see above).
    • Total nail dystrophy: affects all or large proportion of nails associated with chronic mucocutaneous candidiasis. Entire fingernail may become thickened and dystrophic.
  • Diagnosis of above is by direct microscopy.
  • Without treatment, condition often spreads to multiple toenails and can form a portal for recurrent bacterial infections.
  • Common in diabetics and can contribute to foot problems.
  • Treatment is with systemic antifungal agents: terbinafine, itroaconazole, fluconazole.1
  • Need to debride dystrophic nails. In DLSO, remove nail and hyperkeratotic nail bed with clippers. In SWO debride abnormal nail with a curette.
  • Because of slow growth of nails, they do not appear normal even after effective treatment and treatment can be stopped when culture and potassium hydroxide preparations are negative.
  • Patients should practise long term prophylaxis with benzoyl peroxide soap for washing feet, antifungal cream daily, antifungal sprays or powder for shoes.


Paronychia is inflammation of the tissue around the 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 Candida infection but other pathogens, e.g. Pseuodomonas (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, e.g. Staph. aureus and group A Strep.
  • 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.