Dermatophyte infections (Tinea)

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Introduction

Dermatophyte Infections is a superficial fungal infection that affects keratinized tissues.

Fungi that usually cause only superficial
infections on the skin are called
dermatophyte-classified in three genera:

  1. Microsporum,
  2. Trichophyton and
  3. Epidermophyton

It can be acquired from humans, animals, soil or vegetable matter. It is common in tropical climate (which is hot and humid). 

Infection could be spread by fomites. The mycoses caused by dermatophytes are called dermatophytosis, tinea, or ringworm.

On certain parts of the body they have
distinctive features characteristic of that
particular site; therefore the tineas are divided into:

  • Tinea capitis (scalp)
  • Tinea barbae (beard)
  • Tinea manuum (hand)
  • Tinea faciei (face)
  • Tinea corporis (trunk)
  • Tinea cruris (groin
  • Tinea pedis (feet)
  • Tinea unguium or onychomycosis (nail)

Symptoms and clinical features of dermatophyte infections

  • Varied: depending on the site of the body involved
  • Pruritis is a notable symptom

1. Tinea capitis:

  1. Scalp involvement is seen predominantly in children
  2. Lesions are varied in appearance: usually scaly, dry and annular, with or without alopecia
  3. Some appear diffuse and scaly and may involve the whole of the scalp
  4. Inflamed, pustular lesions (kerion) may develop when infection is from animal to man
  5. Pruritus usually leads to excoriation of lesions and secondary bacterial infection
  6. Hypersensitivity to the presence of the fungal elements may occur at distant sites (“Id” reaction).

2. Tinea barbae:

  1. Ringworm of the beard is not a common disease
  2. Occurs chiefly among those in agricultural pursuits, especially those in contact with farm animals
  3. Lesions present as severe, deep folliculitis with erythema, nodular infiltrates, scales and pustules
  4. Marked regional lymphadenopathy
    is the rule.

3. Tinea faciei:

  1. Fungal infection of the face (apart from the beard)
  2. Frequently misdiagnosed, since the typical ringworm not commonly seen on the face
  3. Erythematous, slightly scaling, indistinct borders are usually seen
  4. People who use corticosteroids such as cosmetic bleaching creams are prone to T. faciei
  5. The steroid effect makes the lesions atypical hence, T. incognito.

4. Tinea corporis:

  1. One or more circular, sharply
    circumscribed, slightly  erythematous, dry, scaly patches
  2. Lesions may be slightly elevated, particularly at the borders, where they are more inflamed and scaly than at the central parts
  3. Progressive central clearing produces annular outlines that give them the name “ringworm”
  4. In the presence of immune
    suppression from underlying illness, or chronic use of topical steroid creams lesions may be very extensive and atypical in
    appearance (Tinea incognito).

5. Tinea cruris:

  1. Occurs more commonly in adult men
  2. Leads to severe itching in the groins (crotch)
  3. Presents as slowly spreading erythematous patches with scaly borders on the upper inner aspects of the thighs.

Treatment for dermatophyte infections

Treatment objectives

  • To clear lesions and prevent recurrence

Drug treatment

A. Topical

Ketoconazole

  • 2% cream apply twice daily

Miconazole

  • 2% cream apply twice daily

B. Systemic

Fluconazole

Adult: 50 mg orally daily for 2-4 weeks; up to 6 weeks in tinea pedis

Child:

  • 1 month – 18 years 3 mg/kg (maximum 50 mg) daily for 2-4 weeks; up to 6 weeks in
    tinia pedis

Notable adverse drug reactions

  • Fluconazole: numerous drug interactions
  • Hepatotoxicity during long-term daily therapy

Prevention of dermatophyte infections

  1. Do not share combs, hair brushes, school caps, shoes, socks or underwears
  2. Keep the feet dry; avoid tight-fitting covered shoes
  3. Aerate the feet as often as possible
  4. Use good antiseptic powder on the feet after bathing e.g. Tolnaftate 1% powder
  5. Reduce perspiration and enhance evaporation from the crural areas by wearing loose pants (e.g. boxer pants) made of absorbent cotton fabric
  6. Apply plain talcum powder or antifungal powders in the flexures e.g. armpits, under the breasts, in the groins
  7. Avoid exposure to animals with ringworm (M. canis) especially cats, dogs and (less commonly), horses and cattle
  8. Excessive perspiration is the most common predisposing factor in adult T. corporis
  9. Avoid excessively hot, humid
    environments, or take a cold shower after sweating

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