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Mould infections

Author: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, 2003.

Mould infections — codes and concepts

What are mould infections?

Moulds are organisms found in soil. Those that can infect human skin and nails include:

  • Scopulariopsis brevicaulis
  • Fusarium spp.
  • Aspergillus spp.
  • Alternaria spp.
  • Acremonium spp.
  • Scytalidinum dimidiatum (also known as Hendersonula toruloides, Neofusicoccum mangiferae, Torula dimidiata, Fusicoccum dimidiatum)
  • Scytalidinium hyalinum.

Mould infections cause indolent infections in healthy or immune-compromised individuals. They are more common in older people than in children and young adults. 

Mould infections

What are the clinical features of mould infections?

Mould infections can complicate athlete's foot and appear identical to tinea pedis. They can be mild or severe. Scopulariopsis brevicaulis and Scytalidinum dimidiatum are the most likely moulds to present as a skin infection.

Mould infections of the finger and toenails can be indistinguishable from other types of onychomycosis. However, unlike dermatophyte infections, moulds frequently result in paronychia (inflamed nail folds). One or more toenails may be infected, or the mould may simply be a contaminant. The surrounding skin is often dry and may itch. The appearance of the nail may include:

  • Brownish dull discolouration of the nail, which starts at one edge
  • Streaked and pitted nail plate
  • Complete nail destruction.

How is the diagnosis of mould nail infection made?

Mould infections are diagnosed by microscopy and culture of skin scrapings and/or nail clippings (mycology tests). Culture of moulds is identical to that of dermatophyte fungi except that the antiseptic actidione (cycloheximide) should be left out of the medium.

The infection may be indistinguishable from tinea unguium before mycology has been performed. Sometimes the nails are co-infected by a dermatophyte fungus. If this is so, the laboratory may initially consider the mould a contaminant and fail to report its presence.

Some mould infections are due to dematiaceous fungi (coloured brown) giving rise to phaeohyphomycosis.

Potassium hydroxide examination

What is the treatment for mould nail infections?

Mould nail infections are notoriously difficult to clear with currently available medications, which may be required for longer courses or in combination with other topical and oral antifungal agents.

Cures have been most frequently reported with a combination of:

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