Tinea unguium

• Meissner 1853.
• Virchow 1854.

Onychomycosis

• Fungal infection of the nails.

• If the nail is only infested with dermatophytes, one speaks of a "tinea unguium". If yeast or mould infest the nail (or also in the case of a mixed infection), it is an "onychomycosis".

Categorisation

• Distal subungual onychomycosis (DSOM): most common form.
• Proximal subungual type (PSOM).

• White, superficial onychomycosis (WOOM).

• Onychomycosis caused by moulds.
• Onychomycosis by Candida (Paronychia candidamycetica).

• Total dystrophic onychomycosis.

• Leukonychia trichophytica: whitish, superficial onychomycosis (usually caused by tryichophytes).

• Dystrophic onychomycosis: classic form of chronic mucocutaneous candidosis. 

• Onychia et Paronychia candidosa: usually caused by Candida albicans and is associated with chronic inflammation of the proximal and lateral nail wall. Discolourations and transverse grooves appear.

Immunophenomena in dermatophytosis

• If the human organism is infected by dermatophytes, antibodies are formed in the skin. Evidence can be obtained by means of intradermal testing.

• After injection of (trichophytin) a type I or type IV reaction may occur.

• Incidence (Europe/USA): approx. 20%.
• Incidence (Europe/USA) > 65 years: up to 45%. 

• Causative organism 

  • Approximately 99% of all nail fungal diseases are dermatophytes.

  • Mostly:
  • Trichophyton rubrum (Dermatophyte).

  • Trichophyton mentagrophytes (dermatophyte).

  • Candida albicans.

  • Candida tropicalis (yeast fungus).

  • Scopulariopsis brevicaulis (mould).
  • Aspergillus niger (mould).
  • Hendersonula toruloidea (mould).

• In most cases there is already a tinea pedis. The pathogens enter the nail bed through the hyponychium.
• Candida can cause onychomycosis more often in bakers than in the normal population. The increased moist work and the nutrient supply (glucose from dough) provide a suitable environment for yeast fungi.

• The toenails are affected much more frequently than the fingernails.

• Predisposing factors:

  • Traumas (CAVE too tight/short shoes).

  • Anatomical anomalies.

  • Decreased blood circulation (artierial, venous).

  • Disorders of lymph drainage.

  • Neuropathies.

  • Diabetes mellitus.
  • Immunosuppression.
  • Tinea pedum.

• After the fungi have penetrated into the nail bed via the hyponychium, subununal hyperkeratosis causes the nail plate (onycholysis semilunaris) to lift off.
• A yellow discoloration is called "dyschromasia".

• A "green nail syndrome" is used for secondary infestation with Pseudomonas aeruginosa.

• Crumbnails (onychodystrophy).

• Nail material removal:
• Disinfection with 70% alcohol
• As far proximal as possible!
• Curettage technique
• Native and Culture!
• Histological examination!

With positive findings for moulds:

• Repeat 3 times (only if 3 times no Dermatophytes can be detected, an onychomycosis by moulds can be assumed). 

• Success rate: 50%
• Recurrence rates: 5%-20% and 40% (Grisefulvin)

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