Overview
Tinea Infections
1. Clinical Overview
Summary
Tinea infections (dermatophytosis) are common superficial fungal infections of keratinised tissues (skin, hair, nails) caused by dermatophytes. They are classified by body site: Tinea corporis (body), Tinea pedis (foot), Tinea cruris (groin), Tinea capitis (scalp), and Tinea unguium (nails). The classic presentation is an annular "ringworm" plaque with an active scaly border and central clearing. Diagnosis is often clinical but confirmed by skin scrapings (mycological culture). Most skin infections respond to topical antifungals (terbinafine/azoles), while scalp and nail infections typically require systemic therapy. [1,2]
Key Facts
- Causative Organisms: Trichophyton (most common), Microsporum, Epidermophyton.
- Transmission: Anthropophilic (human-to-human), Zoophilic (animal-to-human - typically more inflammatory), Geophilic (soil).
- Tinea Pedis: "Athlete's foot" - the most common fungal infection globally.
- Tinea Capitis: Commonest cause of patchy hair loss in children. Requires ORAL treatment; creams do not penetrate hair shaft.
- Steroid Danger: Avoid using topical steroids on undiagnosed red rings. It causes "Tinea Incognito" - altered appearance, reduced scaling, but persistent fungal growth.
Clinical Pearls
"Two Feet, One Hand" Syndrome: A classic presentation of Tinea pedis (both feet) and Tinea manuum (one hand - usually the dominant hand used for scratching/picking at feet).
Scrotal Sparing: Tinea cruris (Jock Itch) typically affects the inner thighs but spares the scrotum. If the scrotum is involved, think Candida or eczema.
Tinea Capitis in Kids: Any child with a scaly patch of hair loss or "dandruff" has Tinea Capitis until proven otherwise. Look for enlarged cervical lymph nodes (posterior auricular) - a helpful clue.
The Active Border: The fungus lives in the advancing scaly edge. This is where you scrape for samples. The centre is clearing because the fungus has used up the keratin there.
2. Epidemiology
Incidence
- T. pedis: Affects ~15-25% of the adult population.
- T. capitis: Predominantly children (pre-pubertal). Common in African-Caribbean ethnicity (hair structure susceptibility).
- T. cruris: Adult males > females (anatomy, occlusion).
Risk Factors
- Environment: Warm, humid, moist conditions (occlusive footwear, sweating).
- Contact: Shared showers, swimming pools, combs (fomites).
- Host: Diabetes, Immunosuppression (HIV, Steroids), Atopy.
- Barrier compromise: Maceration of skin.
Organisms
- Trichophyton rubrum: Most common worldwide (70%). Anthropophilic. Chronic infections.
- Trichophyton mentagrophytes: Zoophilic (rodents/pets). More inflammatory.
- Microsporum canis: Zoophilic (cats/dogs). Common cause of Tinea Capitis.
3. Pathophysiology
Mechanism of Infection
- Adherence: Spores adhere to corneocytes (skin cells).
- Invasion: Fungi produce keratinases (enzymes) to digest keratin.
- Colonisation: Hyphae grow within the dead Stratum Corneum. They do NOT typically invade living tissue (epidermis/dermis) unless immunity is compromised.
- Inflammation: Fungal antigens penetrate deeper, triggering Type IV hypersensitivity (redness, itch, scaling).
The "Ring" Formation
- Centrifugal spread: Hyphae grow outwards seeking fresh keratin.
- Central clearing: Core area is depleted of nutrients/immune response clears it.
- Result: Annular plaque.
4. Clinical Presentation
By Site
| Type | Clinical Features |
|---|---|
| Tinea Corporis (Body) | "Ringworm". Single/multiple annular plaques. Erythematous, scaly sharp margin. Central clearing. Itchy. |
| Tinea Pedis (Foot) | Interdigital: Maceration/fissuring between toes (4th/5th). Moccasin: Dry, hyperkeratotic scale over sole/sides. Vesiculobullous: Blisters on instep (often zoophilic). |
| Tinea Cruris (Groin) | "Jock Itch". Well-demarcated plaque on inner thighs. Spares scrotum. Border advances down thigh. |
| Tinea Capitis (Scalp) | Grey patch: Scaling, alopecia, broken hairs. Black dot: Hairs broken at surface. Kerion: Boddy, purulent inflammatory mass (severe reaction). |
| Tinea Manuum (Hand) | Dry, diffuse scaling in palmar creases (hyperkeratosis). Often unilateral. |
| Tinea Unguium (Nail) | Onychomycosis. Yellow/brown discolouration, subungual hyperkeratosis, crumbling nail. |
| Tinea Faciei (Face) | Often atypical, less annular. Can mimic Rosacea/Lupus. |
Red Flags
- Kerion: Severe inflammation on scalp. Risks permanent scarring alopecia. Urgent referral/systemic treatment.
- Majocchi's Granuloma: Deep infection where fungus penetrates down hair follicle into dermis (often after topical steroids). Requires oral treatment.
- Erythroderma: Rare complication of widespread untreated tinea in immunocompromised.
5. Clinical Examination
Assessment
- Distribution: Check feet if body rash present (autoinoculation).
- Morphology:
- "Active border": Scale is usually inward-facing.
- "Central clearing".
- Hair/Nails: Check for scalp scaling, broken hairs (
!), nail dystrophy.
Special Tests
- Wood's Lamp (UV Light):
- Microsporum species fluoresce Green.
- Trichophyton species do NOT fluoresce (most common). Limited utility today.
- Dermoscopy:
- Capitis: "Comma hairs", "Corkscrew hairs".
6. Investigations
Skin Scrapings (Essential for confirmation)
- Method: Scrape the active scaly edge with a scalpel blade onto black paper.
- Nails: Clippings + Subungual debris (scrape under the nail).
- Hair: Pluck hairs with roots + scrape scale (toothbrush method for kids).
Lab Analysis
- Microscopy (KOH mount):
- Potassium Hydroxide dissolves keratin.
- Findings: Branching, septate hyphae and spores.
- Rapid result (24-48h).
- Culture:
- Sabouraud's agar.
- Identifies species (e.g., T. rubrum vs M. canis).
- Takes 2-4 weeks.
When to Swab?
- Generally don't swab. Scrape.
- Bacterial swab only if secondary infection (pus, crusting) suspected.
7. Management
Management Algorithm
SUSPECTED TINEA
( annular scaly rash )
↓
┌─────────────────────────────────────────────┐
│ DETERMINE SITE │
│ - Skin (Body/Groin/Foot) │
│ - Hair (Scalp/Beard) │
│ - Nail │
└─────────────────────────────────────────────┘
↙ ↘
SKIN INFECTION HAIR or NAIL
(Localized) (or Extensive Skin)
↓ ↓
TOPICAL THERAPY ORAL THERAPY
- Terbinafine cream - Terbinafine (Nail/Skin)
- Clotrimazole - Griseofulvin (Scalp - kids)
- Miconazole - Itraconazole
↓ ↓
FAILURE? MONITOR LIVER (If prolonged)
→ Oral Therapy
Topical Therapy (First line for Skin)
- Terbinafine (Lamisil): Fungicidal. 1-2 weeks. Most effective.
- Azoles (Clotrimazole, Miconazole, Ketoconazole): Fungistatic. Require 4 weeks treatment (continue 2 weeks after rash clears).
- Steroid combinations (e.g., Daktacort): Use with caution. Only for first few days to reduce itch, then switch to pure antifungal.
Oral Therapy (Systemic)
- Indications: Tinea Capitis, Onychomycosis, Extensive/Resistant skin tinea, Majocchi's granuloma.
Drugs:
- Terbinafine (Oral):
- Gold standard for Dermatophytes.
- Dose: 250mg OD.
- Duration: Skin (2-4 weeks), Fingernails (6 weeks), Toenails (12 weeks).
- Monitor: LFTs (rare hepatotoxicity).
- Itraconazole:
- Alternative or "Pulse therapy" for nails.
- Broad spectrum (covers Candida too).
- Griseofulvin:
- Historically used for Tinea Capitis in children (licensed).
- Long courses required (8-12 weeks).
- Taken with fatty food.
Specific Management by Site
| Condition | Primary Treatment | Notes |
|---|---|---|
| Tinea Pedis | Topical Terbinafine | Treat shoes (fungal spores survive). |
| Tinea Corporis | Topical Terbinafine | Wash clothes at 60°C. |
| Tinea Capitis | Oral Griseofulvin or Terbinafine | Add Ketoconazole shampoo to reduce shedding. Treat household contacts if symptomatic. |
| Onychomycosis | Oral Terbinafine (12wks) | Topicals (Loceryl) low cure rate (less than 50%) - use only for superficial/mild. |
8. Complications
- Bacterial Superinfection: Cellulitis (especially leg cellulitis from tinea pedis entry point).
- Id Reaction: Immunological reaction. Widespread itchy blisters on fingers/body in response to tinea infection elsewhere (e.g., foot).
- Permanent Alopecia: Kerion (Tinea Capitis).
- Tinea Incognito: Modified, difficult-to-diagnose tinea after steroid use.
- Psychosocial: Onychomycosis can be unsightly.
9. Prognosis and Outcomes
Cure Rates
- Skin: High (>90%) with correct treatment.
- Nails: Lower. Oral terbinafine cure ~70-75%. Recurrence is common (20-50%).
- Scalp: High if compliant with oral therapy.
Recurrence
- Common, especially Tinea Pedis.
- Prevention: Dry toes, breathable socks, flip-flops in showers, changing shoes.
10. Evidence and Guidelines
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| Fungal Skin Infections | BAD / PHE | Specimen collection before oral treatment. Terbinafine drug of choice. |
| Onychomycosis | British Assoc. Dermatologists | Oral terbinafine superior to itraconazole and fluconazole. |
| Tinea Capitis | BAD | Griseofulvin or Terbinafine. Treat contacts. |
Landmark Studies
1. Cochrane Review (Crawford et al, 2007) [5]
- Question: Topical treatments for Tinea Pedis.
- Result: Allylamines (Terbinafine) are superior to Azoles producing higher cure rates in shorter time.
- Impact: Terbinafine is first choice if cost permits.
2. The TOESTRUDY (sigurgeirsson et al)
- Question: Onychomycosis treatment.
- Result: Terbinafine continuous vs Itraconazole pulse. Terbinafine higher mycological cure (76% vs 63%).
- Impact: Terbinafine remains gold standard for nails.
11. Patient and Layperson Explanation
What is Ringworm?
It is NOT a worm. It is a fungal infection of the skin. It is called "ringworm" because it often causes a red, ring-shaped rash with a scaly edge.
Where can I get it?
- Body: Ringworm.
- Feet: Athlete's Foot.
- Groin: Jock Itch.
- Scalp: Ringworm of the scalp.
How did I catch it?
- From other people (skin contact, sharing towels/combs).
- From animals (cats, dogs, guinea pigs).
- From the soil (rare).
- Athlete's foot is often caught in gym showers or pools.
How do I treat it?
- Creams: Most skin rashes clear up with antifungal creams (like lamisil or canesten) used for 1-4 weeks. Keep using it for a week after the rash has gone to make sure.
- Tablets: Fungal nail infections and scalp infections usually need tablets for several weeks or months, as creams can't reach deep enough.
How do I stop it coming back?
- Keep skin dry (unexpectedly fungi love damp warm places).
- Dry between your toes carefully.
- Don't share towels.
- Wash clothes/bedding at 60°C to kill spores.
- Treat pets if they have patches of hair loss.
12. References
Primary Sources
- Sahoo AK, Mahajan R. Management of tinea corporis, tinea cruris, and tinea pedis: A comprehensive review. Indian Dermatol Online J. 2016;7:77-86. PMID: 27057486.
- Ely JW, et al. Diagnosis and Management of Tinea Infections. Am Fam Physician. 2014;90:702-710. PMID: 25403034.
- Public Health England. Fungal skin and nail infections: diagnosis and management. 2024.
- Ameen M, et al. British Association of Dermatologists' guidelines for the management of onychomycosis 2014. Br J Dermatol. 2014;171:937-958. PMID: 25222920.
- Crawford F, Hollis S. Topical treatments for fungal infections of the skin and nails of the foot. Cochrane Database Syst Rev. 2007;CD001434. PMID: 17636672.
13. Examination Focus
Common Exam Questions
- Paediatrics: "A 6-year-old child has a patch of hair loss with scaling. What is the treatment?"
- Answer: Oral antifungal (Griseofulvin/Terbinafine). Topical is ineffective.
- General Practice: "Patient with itchy groin rash, scrotum is spared. Diagnosis?"
- Answer: Tinea Cruris. (Candida affects scrotum).
- Dermatology: "What is the cause of scattered itchy vesicles on fingers in a patient with athlete's foot?"
- Answer: Id reaction (Dermatophytid).
- Pharmacology: "Mechanism of Terbinafine?"
- Answer: Inhibits squalene epoxidase (ergosterol synthesis inhibitor).
Viva Points
- Tinea Incognito: Appearance modifies by steroids. Less scale, more diffuse, pustules.
- Kerion: Severe host response. Boggy mass. Need to treat inflammation (sometimes add steroids) + kill fungus.
- Diagnosis: Why scrape the edge? That's where the active hyphae are.
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.