Clinical Notes : Dermatology

141. Tinea Nigra

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Tinea infections

"Tinea" refers to a skin infection with a dermatophyte (ringworm) fungus.

Depending on which part of the body is affected, it is given a specific name :

Sometimes, the name gives a different meaning :

  • Tinea versicolor is more accurately called pityriasis versicolor. This is a common yeast infection on the trunk.

  • Tinea incognita (often spelled incognito) refers to a tinea infection in which the clinical appearance has changed because of inappropriate treatment.

  • Tinea nigra is a mould infection (not a dermatophyte). It affects the palms or soles, which appear brown (on white skin) or black (on dark skin).

Clinical variants include :

  • Tinea imbricata

  • Majocchi granuloma

  • Kerion

  • Favus

 

What is Tinea Nigra ?

Tinea nigra affects the skin of the palm and/or sole with persistent slowly growing brown or black patches.

They are slightly scaly and do not itch or sting.

Tinea nigra is most common in tropical regions and often infects those with a tendency to excessive sweating (hyperhidrosis).

Tinea nigra is due to infection with a brown mould : Exophiala phaeoannellomyces. This mould usually inhabits soil.

The organism's other names include:

  • Hortaea werneckii

  • Phaeoannellomyces werneckii

  • Exophiala werneckii

  • Cladosporium werneckii

 

The infection is sometimes confused with other skin conditions such as:

  • Melanoma

  • Benign moles (naevi)

  • Stains

  • Pigmentation arising after a dermatitis or other skin inflammation

Tinea nigra

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Laboratory tests

Scrapings taken from the edge of the scaly lesion show mycelium (a group of branched filaments or hyphae).

The hyphae can be clear in colour, yellow or brown and are septate (this means they are divided into compartments by thick walls).

 

Culture grows black colonies of Phaeoannellomyces wernekii within a week.

The diagnosis may also be made on skin biopsy because of characteristic histopathological features of tinea nigra.

Treatment of tinea nigra

 

Tinea nigra usually clears with topical antifungal applied for 2 -4 weeks.

 
 

Tinea Nigra

DermNetNZ  (CCPL)

2003

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