Tinea (Dermatophytes)

Summary

Tinea refers to a group of superficial fungal infections caused by dermatophyte fungi, most commonly species of Microsporum, Trichophyton, and Epidermophyton. These infections typically present as annular (ring-shaped) scaly plaques, often accompanied by pruritus (itching). Tinea is classified by the body site involved: tinea capitis (scalp), tinea corporis (body), tinea cruris (groin), tinea pedis (feet), and tinea unguium (nails; also called onychomycosis).

Diagnosis can be made in two main ways: (1) Wood’s lamp examination – some species (especially Microsporum) cause infected hairs to fluoresce green, and (2) Microscopy – potassium hydroxide (KOH) preparation with a blue fungal stain can reveal branching, septate hyphae.

Treatment options include fluconazole, terbinafine, and griseofulvin. Griseofulvin is effective because it inhibits fungal mitosis and binds to keratin, allowing it to concentrate in skin, hair, and nails where dermatophytes grow.

Key Points

• Tinea
  • Characteristics
    • Fungal cutaneous (skin) infections
    • Dermatophytes implicated
      • Microsporum
        • Animal contact associated with Microsporum
      • Trichophyton
      • Epidermophyton
  • Presentation
    • Presents with ring-like (annular) scaling plaques
      • Well-demarcated, raised erythematous borders, with central clearing
    • Associated with pruritus (itchiness)
    • Diseases named for part of the body they affect
    • Tinea capitis = head/scalp
      • Pruritic lesions on scalp
      • Most common in pre-pubertal boys
      • Acquired through direct contact with fungus
    • Tinea corporis = body
      • Occurs on body (usually torso)
      • Can be acquired from contact with infected pets or farm animals
        • Classically in athletes with skin-to-skin contact (wrestlers) (mb)
    • Tinea cruris = groin
      • Also known as “jock itch”; occurs in inguinal area
    • Tinea pedis = foot
      • Also known as “athlete’s foot”
      • Seen with occlusive footwear or barefoot walkers
    • Tinea unguium = nails
      • Type of onychomycosis (fungal nail infection)
      • Thickened nails with white, yellow, or brown discoloration
  • Diagnosis
    • Branching septate hyphae visible on KOH preparation with blue fungal stain
    • Wood’s lamp exam reveals green fluorescence of infected hairs
  • Treatment
    • Topical or oral antifungals used, depending on severity
    • Azoles (fluconazole)
    • Terbinafine
      • Inhibits squalene epoxidase, which inhibits synthesis of ergosterol needed for fungal membrane
    • Griseofulvin
      • Inhibits fungal mitosis and binds to keratin
    • Operative treatment may be required for deep nail infections