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Fungal Skin and Nail Infections (Tinea)

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Overview

Tinea describes a fungal infection of keratinised tissues (e.g. hair, skin, and nails) due to dermatophytes.

  • Tinea pedis describes an infection of the feet (also known as athlete’s foot)
  • Tinea capitis describes an infection of the scalp (also known as scalp ringworm)
    • Commonly caused by Trichophyton tonsurans
  • Tinea corporis describes an infection of the trunk, arms, or legs (also known as ringworm)
    • Commonly caused by Trichophyton rubrum or Trichophyton interdigitale
  • Tinea cruris describes an infection of the groin
    • Often due to autoinoculation of other dermatophyte infections including the other types of tinea
  • Tinea unguium describes an infection of the nail (also known as onychomycosis):
    • Often due to Trichophyton rubrum and associated with adjacent skin infections

Transmission

Transmission is via direct contact or fomites, leading to the spread of fungal spores which can germinate and grow down the hair shaft and penetrate the hair.

Epidemiology

  • Tinea is most commonly seen in children and young adults
  • Tinea is more common in men than women
  • Tine cruris is more common in adolescents and young adult men
  • Tinea capitis is more common in prepubertal children with a peak incidence between 3-7 years old and is more common in Afro-Caribbean than white children
  • Incidence is lower in adults but may be seen in people with immunocompromise

Risk Factors

  • Hot, humid climates
  • Tight-fitting clothing
  • Hyperhidrosis
  • Immunocompromised states – such as HIV and immunosuppressive drugs
  • Diabetes mellitus
  • Obesity
  • Existing skin disorders (e.g. psoriasis)

Presentation

Tinea capitis

Features of tinea capitis include:

  • Scalp scaling appearing similar to dandruff and hair loss
  • If untreated, a raised, spongy or boggy lesion can appear in a bald area, known as a kerion
    • This is an abscess that occurs due to inflammation in response to tinea capitis
    • It is tender and may ooze

Tinea corporis and tinea cruris

Features of tinea corporis include:

  • Well-defined, erythematous, concentric rings of scales (annular lesions)
    • They develop central clearing as the rash expands
    • The edges may appear raised
    • They may be pruritic

Tinea cruris has similar features seen in the groin and sometimes the scrotum.

Tinea pedis

Features of tinea pedis:

  • Maceration, scaling, flaking, and pruritus between the toes
  • Toe web fissures (interdigital erosions) – cracking of the skin between the toes

Tinea unguium (onychomycosis)

Many people may say they have ‘unsightly nails’. Features of tinea unguium (onychomycosis) include:

  • Thick, discoloured (e.g. white, yellow, brown, black), opaque nails
  • Onycholysis may be present
  • An associated adjacent skin infection

Diagnosis

Diagnosis is often made clinically, however, skin sampling for microscopy and culture may be performed if the diagnosis is uncertain, the presentation is atypical, or the disease is severe/extensive.

For onychomycosis, nail clippings/scrapings should be taken for microscopy and culture if antifungal treatment is being considered.

Management

Overview

The management of tinea capitis includes

  • 1st-line: oral antifungals such as terbinafine or griseofulvin
  • To reduce transmission risk: consider topical ketoconazole shampoo

The management of tinea corporis, tinea pedis, and tinea cruris includes:

  • If mild: topical antifungals (e.g. terbinafine or clotrimazole creams)
    • If there is associated marked inflammation: consider adding topical hydrocortisone
  • If severe/extensive: oral antifungals (e.g. oral fluconazole)

The management of tinea pedis includes:

  • 1st-line: topical imidazole

The management of tinea unguium (onychomycosis) includes:

  • 1st-line: oral antifungals (oral terbinafine) as topical therapy rarely works
  • If ineffective: oral itraconazole may be used

Complications

Secondary bacterial infection – skin breaks and maceration can lead to bacterial infection, often by Streptococcus species, and can cause impetigo and cellulitis.

Skin changes and hair loss – skin changes include pigmentation changes, scarring, and damage.

Kerion – a raised, spongy or boggy lesion that appears in an affected area due to an abscess forming secondary to inflammation. It is tender and may ooze.

Autoinoculation infections – infections of other sites may occur, such as tinea manuum (a fungal infection of the hand), which can occur as a result of scratching affected areas.

Tinea incognito – inappropriate topical corticosteroid use can lead to increased spread of the fungal infection and a change in its shape, resulting in it mimicking other skin conditions, hence its name. It is also known as steroid-modified tinea. It may become less scaly, lose its annular appearance, and become pustular.

Prognosis

  • In most people, effective treatment has an excellent prognosis
  • Delays in diagnosis and treatment and immunosuppression are associated with an increased risk of complications and severe disease.

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