Differential diagnoses - Conditions affecting the nails

Dr Nigel Stollery compares four presentations and offers clues for their diagnosis.



  • Very common cause of discoloured and dystrophic nails
  • Toenails more commonly affected than fingernails
  • Caused by a fungal or yeast infection, most commonly Trichophyton rubrum
  • Nail often becomes thickened and may be difficult to cut


  • Diagnosis can be confirmed by microscopy
  • Treatment unnecessary in most cases
  • A course of an oral antifungal for three to six months is required
  • Recurrence after treatment not uncommon
  • Nail varnish is an alternative to treatment



  • Thickened dystrophic nail, usually caused by self-neglect
  • Surface of nail may be ridged
  • May also occur secondary to trauma or peripheral vascular disease
  • In most cases, toenails affected rather than fingernails
  • In fingernails, usually only a single nail is affected
  • More common in the elderly
  • May be quite painful and debilitating


  • Treatment usually undertaken by podiatrists, who are able to file and cut the nails
  • With continuing chiropody, should not recur



  • Relatively common condition
  • Separation of the nail from the nail bed
  • Usually starts distally and extends proximally, except in psoriasis
  • Causes include psoriasis, circulation problems such as Raynaud's and thyroid disease
  • May occur as a side-effect of medication, for example, tetracyclines


  • Treatment can be difficult
  • Keeping nails short should help
  • Secondary infection may occur, which can be treated with antifungals or antibiotics



  • Affects fingernails and toenails
  • Changes occurring with psoriasis include surface pitting, onycholysis and subungual hyperkeratosis
  • Nail psoriasis occurs in about 50% of patients with psoriasis
  • Can rarely occur without skin psoriasis


  • Diagnosis usually clinical
  • Management includes keeping nails short and avoiding false nails and moisture
  • Treatment can be difficult and includes topical steroids
  • In severe cases, oral treatment such as methotrexate can be helpful.

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