Tinea Corporis

Tinea corporis (body ringworm)

Introduction

Tinea corporis is a superficial fungal infection (dermatophytosis) of the glabrous (non-hairy) skin of the body. It commonly affects the arms, legs, trunk, and neck but may occur on any part of the body except the scalp, groin, palms, and soles. It is commonly referred to as ringworm of the body because of its characteristic ring-shaped appearance.

The condition is contagious and occurs worldwide, particularly in warm and humid climates.

Etiology

Tinea corporis is caused by dermatophytes including:

• Trichophyton species (most common)

• Microsporum species

• Epidermophyton floccosum

Sources of infection include:

• Human-to-human transmission

• Contact with infected animals (cats, dogs, cattle)

• Contact with contaminated soil

Risk factors

• Hot and humid climate

• Excessive sweating

• Poor hygiene

• Crowded living conditions

• Contact sports (e.g. wrestling)

• Close contact with infected persons or animals

• Sharing towels or clothing

• Diabetes mellitus

• Immunosuppression

Children and young adults are commonly affected.

Pathophysiology

Dermatophytes infect keratinized tissues by:

• Adhering to the stratum corneum

• Producing keratinase enzymes that digest keratin

• Growing centrifugally, resulting in peripheral expansion

• Central clearing occurring as the immune response controls infection centrally

This produces the characteristic annular lesion with an active scaly border.

Clinical presentation

Typical features include:

• Enlarging raised annular lesions with central clearing

• Well-defined erythematous border

• Fine peripheral scales

• Pruritus (itching)

• Hair loss in affected areas when hair follicles are involved

Other findings may include:

• Multiple lesions that coalesce

• Vesicles along the advancing border

• More extensive lesions in immunocompromised patients

• More inflammatory lesions with pustular borders, particularly following animal exposure

Diagnostic criteria

Diagnosis is primarily clinical and is supported by:

• Annular raised lesions

• Central clearing

• Peripheral scaling

• Progressive outward expansion

• Pruritus

• Presence of relevant risk factors

Differential diagnosis

• Nummular eczema

• Psoriasis

• Pityriasis rosea

• Granuloma annulare

• Seborrheic dermatitis

• Cutaneous lupus erythematosus

Investigations

Typical cases usually do not require laboratory confirmation.

When necessary, perform:

• Skin scraping from the advancing edge of the lesion for potassium hydroxide (KOH) microscopy

• Fungal culture to identify the dermatophyte species

• Wood's lamp examination when Microsporum infection is suspected

• Skin biopsy in atypical or difficult cases

Treatment

Non-pharmacological treatment

• Keep the affected skin clean and dry

• Avoid tight clothing

• Avoid sharing towels and clothing

• Wash contaminated clothing separately

• Treat infected household pets where applicable

• Avoid scratching lesions

• Maintain good personal hygiene

• Optimize control of diabetes mellitus

Pharmacological treatment

Localized disease

• Benzoic acid compound ointment (topical), apply every 12 hours for up to 2 weeks

OR

• Miconazole cream 2% (topical), apply a thin layer every 12 hours and continue for 5–7 days after complete clearance of lesions

OR

• Terbinafine cream (topical), apply every 12 hours for 2 weeks

Extensive or refractory disease

• Terbinafine (PO) 250 mg once daily for 2 weeks

Systemic therapy should be considered for:

• Extensive disease

• Multiple widespread lesions

• Failure of topical therapy

• Follicular involvement

• Immunocompromised patients

Complications

• Secondary bacterial infection

• Chronic recurrent infection

• Post-inflammatory hyperpigmentation

• Spread to other body sites

• Tinea incognito following inappropriate topical corticosteroid use

Prevention

• Avoid sharing towels, clothing, and personal items

• Treat infected household pets

• Keep the skin dry

• Wear loose, breathable clothing

• Treat lesions promptly

• Avoid unnecessary use of topical corticosteroids

• Promote good hygiene, particularly in schools and sports teams

Prognosis

• Most patients recover completely with appropriate treatment within 2–4 weeks.

• Recurrence is common if predisposing risk factors persist or treatment is incomplete.