What are the different types of tinea infections and their characteristics?

Types of Tinea Infections and Their Characteristics

Tinea infections are superficial fungal infections caused by dermatophytes that affect different parts of the body with distinct clinical presentations and treatment approaches. 1

Common Types of Tinea Infections

Tinea Corporis (Ringworm)

• Affects the general skin of the body, typically presenting as circular, erythematous, scaly patches with central clearing and raised borders 2
• Most commonly caused by Trichophyton rubrum and other dermatophyte species 1
• Treatment typically requires 2-4 weeks of topical antifungal agents such as terbinafine cream or butenafine cream 3

Tinea Cruris (Jock Itch)

• Affects the groin area, presenting as erythematous patches with scaling that may extend to the inner thighs 2
• More common in adolescents and adults, particularly males 1
• Usually treated with topical antifungals for two weeks, with azoles or allylamines being effective options 3

Tinea Pedis (Athlete's Foot)

• Affects the feet, particularly between the toes and soles 1
• Presents in several forms:
  • Interdigital: maceration and scaling between toes
  • Moccasin-type: chronic hyperkeratosis and scaling of the soles
  • Vesicular: inflammatory vesicles on the instep or soles 3
• Treatment typically requires 4 weeks with azole antifungals or 1-2 weeks with allylamine medications 3
• Associated with increased risk in athletes and swimmers due to trauma, sweating, and exposure to infectious dermatophytes 4

Tinea Capitis (Scalp Ringworm)

• Infection of scalp hair follicles and surrounding skin 4
• More common in pre-pubertal children 5
• Clinical presentations include:
  • Non-inflammatory: diffuse scaling resembling dandruff
  • Inflammatory: diffuse pustular lesions with patchy alopecia and painful regional lymphadenopathy
  • Kerion: painful, boggy, inflammatory mass with pustules and thick crust 4
  • Favus: chronic inflammatory variant with yellow, crusted, cup-shaped lesions ("scutula") around follicular openings 4
• Oral antifungal therapy is required, with griseofulvin being the first-line treatment for 4-6 weeks at 10 mg/kg/day for children 6

Tinea Unguium (Onychomycosis)

• Fungal infection of the nail apparatus affecting the nail bed and plate 4
• More common in toenails (80% of cases) than fingernails 4
• Clinical presentations include:
  • Distal and lateral subungual onychomycosis (DLSO): most common form, affecting the hyponychium and lateral edges initially, causing subungual hyperkeratosis and onycholysis 4
  • Superficial white onychomycosis (SWO): affects the surface of the nail plate with white discoloration and flaky appearance 4
  • Proximal subungual onychomycosis (PSO): uncommon variant often associated with immunosuppression 4
• Treatment requires prolonged oral antifungal therapy: at least 4 months for fingernails and 6 months for toenails 6

Special Populations and Risk Factors

Children

• Tinea capitis is the most common dermatophyte infection in children 1
• Onychomycosis is less common but increasing in prevalence, representing 15% of nail dystrophies in children 4
• T. rubrum is the most prevalent species in childhood onychomycosis, followed by T. tonsurans 4

Athletes

• Higher prevalence of tinea infections, especially tinea pedis and onychomycosis 4
• Predisposing factors include:
  • Sports-related trauma to nails and feet
  • Previous tinea pedis infection
  • Increased sweating
  • Use of synthetic clothing and shoes that retain sweat
  • Water sports and communal bathing 4

Diabetics

• Almost three times more likely to develop onychomycosis than non-diabetics 4
• Higher risk of complications due to poor circulation, neuropathy, and impaired wound healing 4
• Diseased nails with thick sharp edges can injure surrounding skin, creating entry points for pathogens 4

Diagnostic Approach

• Clinical appearance is suggestive but unreliable due to many mimics 1
• Confirmation with laboratory testing is essential before starting treatment 6
• Diagnostic methods include:
  • Direct microscopy with potassium hydroxide (KOH) preparation
  • Culture on appropriate medium (e.g., Sabouraud agar)
  • In some cases, nail biopsy or histologic examination 6

Treatment Principles

• Treatment duration must continue until the infecting organism is completely eradicated 6
• General hygiene measures should be observed to control sources of infection or reinfection 6
• Topical therapy is generally successful for limited infections, while extensive disease may require systemic therapy 3
• Treatment should continue for at least one week after clinical clearing of infection 3

Common Pitfalls and Caveats

• Clinical diagnosis can be unreliable as many conditions mimic tinea infections:
  • Tinea corporis can be confused with eczema
  • Tinea capitis can be confused with alopecia areata
  • Onychomycosis can be confused with dystrophic toenails from trauma 1
• Failure to confirm diagnosis with laboratory testing may lead to inappropriate treatment 6
• Untreated tinea can cause significant morbidity and predispose to complications, including cellulitis, ulcers on the feet, and permanent alopecia on the scalp 5
• Kerion should be treated promptly to prevent scarring and permanent hair loss 1