🦷 Ringworm (Tinea Corporis) Diagnosis Simulator

The Annular Lesion — Ringworm on Physical Exam

Placeholder: classic ring-shaped lesion, active border, clearing center.

• Annular: Shape (ring with central clearing)
• Raised, scaly: Border (active leading edge)
• Centrifugal: Growth (expands outward over weeks)
• Trunk, limbs: Common sites (exposed, warm-moist skin)

What the lesion looks like

Placeholder text: ring-shaped plaque, scaly active edge, clear healing center.

Why the border stays active

Placeholder text: fungus spreads outward, immune response clears the center.

Wood's Lamp — Fast Screen, Limited Sensitivity

Placeholder: UV light can help, but many dermatophytes stay dark.

• ~365 nm: Wavelength (long-wave UV-A lamp)
• Fluoresce: Microsporum spp. (apple-green glow)
• Usually dark: Trichophyton spp. (most common cause, no glow)
• Low: Overall sensitivity (cannot rule out tinea alone)

How the test works

Placeholder text: darkened room, UV lamp held near lesion, glow noted.

Why it can mislead

Placeholder text: negative glow does not exclude tinea corporis.

KOH Prep — The Definitive Bedside Test

Placeholder: scraping dissolved in KOH reveals hyphae under the scope.

• Active border: Sample site (highest fungal density)
• 10–20% KOH: Reagent (dissolves keratin, not hyphae)
• Septate hyphae: Positive finding (branching, uniform width)
• Minutes: Turnaround (bedside microscope read)

Collecting the sample

Placeholder text: scalpel scrapes scale from the active advancing edge.

Reading the slide

Placeholder text: branching septate hyphae cross skin cell borders.

Ringworm vs. Nummular Eczema

Placeholder: eczema mimics ringworm but fails every fungal test.

• Uniform patch: Eczema shape (no central clearing)
• Not raised: Eczema border (diffuse, ill-defined edge)
• Negative: Eczema Wood's lamp (no fluorescence ever)
• Negative: Eczema KOH (no hyphae, only skin cells)

Key visual differences

Placeholder text: coin-shaped uniform plaques, itchy, symmetric distribution.

Why testing still matters

Placeholder text: overlap in appearance makes KOH prep essential.

Confirmed Diagnosis Guides Treatment

Placeholder: positive hyphae confirm tinea, steer therapy correctly.

• KOH positive: Confirmatory test (septate branching hyphae)
• Topical antifungal: Correct treatment (terbinafine, clotrimazole)
• Topical steroids: Avoid (can worsen tinea (incognito))
• Emollients/steroids: Eczema treatment (if KOH negative)

From microscope to prescription

Placeholder text: hyphae seen, diagnosis confirmed, antifungal started.

Why the distinction matters

Placeholder text: steroids on tinea can mask and worsen the fungus.

Placeholder highlight: never treat an undiagnosed ring with steroids alone.