Dermatophytosis (Tinea)

Dermatophytosis (tinea) infections are fungal infections caused by dermatophytes - a group of fungi that invade and grow in dead keratin. Several species commonly invade human keratin and these belong to the Epidermophyton, Microsporum and Trichophyton genera. They tend to grow outwards on skin producing a ring like pattern, hence the term 'ringworm'. They are very common and affect different parts of the body. They can usually be successfully treated but success depends on the site of infection and on compliance with treatment.

• Infection is limited to the dead layers of skin but encouraged by a damp and warm local environment.
• The infection can be transmitted to humans by anthropophilic (between people), geophilic (from soil) and zoophilic (from animals) spread.
• The most common organisms are:
  • Trichophytons rubrum, tonsurans, interdigitale and mentagrophytes
  • Microsporum canis
  • Epidermophyton floccosum
• Clinical classification is according to site:
  • Scalp - tinea capitis
  • Feet - tinea pedis
  • Nail - tinea unguum (or onychomycosis)
  • Beard area - tinea barbae
  • Groin - tinea cruris
  • Body including trunk and arms- tinea corporis

Infection is very common all over the world. Some types are more common than others with tinea pedis being most common in adults and tinea capitis the most common in children. Onychomycosis is also extremely common affecting about 3% of men and 1.5% of women. Tinea cruris occurs much more often in men because of the scrotal anatomy. T rubrum is the most common organism worldwide.

History

• Itching, rash and nail discolouration are the most common symptoms of tinea infection.
• Hair loss occurs with tinea capitis (mainly a disease of children).
• Complications such as secondary infection (cellulitis and impetigo) can lead to symptoms.
• It is common in people who play contact sports.
• It occurs in immunocompromised patients.

On examination

• Tinea pedis:
  • It affects particularly the web of the toe where skin may be macerated and erythematous.
  • It commonly affects plantar surface of the foot. Erythema, vesicles and pustules can occur.
  
• Tinea capitis¹:
  • It can cause hair loss with broken hairs at the surface (as distinct from alopecia areata).
  • Clinical appearance is variable.
• Tinea unguum (onychomycosis):
  • Onycholysis or separation of the nail from the nail bed commonly occurs.
  • Nail dystrophy with thickening and discolouration of the nail develops.
• Tinea corporis:
  • The skin lesions have annular scaly plaques with raised edges.
  • There may be vesicles and pustules.
  • Typically lesions are on exposed skin of trunk, arms and legs (see differential diagnosis).
  
• Tinea manuum:
  • Usually with tinea pedis.
  • Typically just affects one hand.
  • Scaling and redness are prominent.
  • Incorrect diagnosis and use of steroid may eventually exacerbate the infection.
  
• Tinea cruris:
  • Usually occurs in men.
  • Often tolerated for some time before presentation.
  • Typically erythematous with central clearing and raised edge.
• Tinea barbae:
  • Affects the beard area.
  • Redness, scaling and pustules are common.

Other annular rashes are often confused with tinea infections. Eczema and psoriasis are commonly confused with tinea. Pityriasis versicolor occurs all over the trunk while candida occurs as a flexural rash at extremes of age or in the immunocompromised, diabetic or patients on antibiotics.Treatment with topical steroids often causes confusion making tinea less scaly and more erythematous. Steroid use also makes the 'active' edge and the inactive centre less distinct (tinea incognito). Clinically the diagnosis can be difficult, but if it is a possibility take scrapings for mycology. Other fungal infections look nothing like tinea. Other conditions to consider include:

• Contact dermatitis
• Seborrhoeic dermatitis
• Intertrigo
• Erythrasma
• Mycosis fungoides
• Alopecia areata

• Microscopy of skin and nail specimens may reveal hyphae and spores.
• Fungal culture can identify the species but is not always reliable and it can take 6 weeks to get results.
• Ultraviolet light (Wood light) is useful for tinea capitis especially. Fluorescence is produced by the fungus.

Immunocompromised states, atopy and Cushing syndrome have all been associated with fungal infections.

• For most skin infections it is sufficient to apply an imidazole cream twice daily. Treatment is continued for 1-2 weeks after the skin has healed:
  • Clotrimazole
  • Econazole
  • Ketoconazole
  • Miconazole
  • Sulconazole
  Terbinafine (Lamisil) cream daily is also effective but much more expensive. It usually requires only 1 week of treatment topically.If this fails to clear (recheck mycology - if negative reconsider diagnosis).
• Clotrimazole or miconazole is recommended topically for pregnant or breast feeding women.
• Agents containing a corticosteroid are not usually necessary. They may be used if there is a lot of skin inflammation.
• Offer advice on hygiene measures:
  • Continue school and sports activities
  • Cover feet in communal changing areas
• Systemic agents are appropriate for tinea capitis¹ and onychomycosis (although topical nail preparations can be used in limited distal nail disease). They should be used for extensive disease.They may also be used when topical treatments have failed or are inappropriate. Skin scrapings should be sent before starting oral treatment.
  • Griseofulvin 500 mg daily in adults. 10 mg/kg daily in children for tinea capitis particularly.
  • Terbinafine 250 mg daily for 2 weeks (up to 6 weeks).
  • Itraconazole 100 mg twice daily for 1 week (high dose for 1 week or low dose for 30 days).
• Referral may be needed if diagnosis is in doubt.

The main complication is secondary bacterial infection. Hair loss is a complication of tinea capitis. Pain and difficulty with shoes can result from onychomycosis.

Excellent with good compliance and subsequent precautions to avoid repeat infection.

• Good skin hygiene
• Good nail hygiene
• Avoiding prolonged wetting or dampness of skin and feet