DR7.1-2 | Fungal Infections — Practice Quiz

Correct. The active advancing border has the highest density of fungal hyphae. The central cleared area has fewer organisms because the host immune response has partially cleared the infection there.

For annular dermatophyte lesions, always scrape the active raised advancing border, not the central cleared area. Fungal elements are most abundant at the edge where active invasion is occurring.

The correct answer is the active raised border. Dermatophytes concentrate at the advancing edge of the lesion. Scraping the cleared centre — the most common error — yields false negatives because organisms have already been cleared by the immune response.

Correct. Short, stubby, curved hyphae with clusters of round spores ('spaghetti and meatballs') on KOH is the hallmark of Malassezia furfur causing pityriasis versicolor.

The 'spaghetti and meatballs' (or 'banana and grapes') pattern on KOH — short curved hyphae with clusters of round spores — is pathognomonic for Malassezia furfur in tinea versicolor.

The 'spaghetti and meatballs' appearance is pathognomonic for Malassezia furfur (tinea versicolor). Dermatophytes show long, branching, septate hyphae. Candida shows pseudohyphae with budding yeast.

Correct. Tinea cruris spares the scrotum (unlike candidal intertrigo). Topical azoles (clotrimazole, miconazole) or topical terbinafine are first-line for limited disease. KOH confirming septate hyphae establishes the dermatophyte diagnosis.

Tinea cruris involves the groin-thigh junction with inguinal sparing of scrotum (unlike Candida which involves the scrotum). First-line is topical azole (clotrimazole/miconazole) or topical terbinafine for 2–4 weeks for limited disease.

This is tinea cruris (groin dermatophytosis), confirmed by septate hyphae on KOH. Topical azoles (clotrimazole or miconazole) are first-line for limited disease. Oral therapy is reserved for extensive, recurrent, or nail disease.

Correct. Candida albicans on KOH shows pseudohyphae (elongated chains of blastospores) with budding yeast cells. This distinguishes it from true dermatophyte hyphae (which are septate and truly filamentous) and from Malassezia.

Oral candidiasis (thrush) is caused by Candida albicans. KOH of scrapings shows pseudohyphae (chain-like elongated blastospores) along with budding yeast cells. The scrapable white plaques are characteristic.

Candida on KOH shows pseudohyphae with budding yeast cells — not true septate hyphae (dermatophytes) or spaghetti-and-meatballs (Malassezia). Pseudohyphae are elongated blastospores that form chains but retain constrictions at the septa.

Correct. Microsporum species fluoresce bright green (yellow-green) under Wood's lamp due to pteridine metabolites. Trichophyton species (responsible for most tinea capitis in India today) are Wood's lamp negative — an important clinical distinction.

Microsporum species (M. canis, M. audouinii) cause ectothrix tinea capitis and show bright green (yellow-green) fluorescence on Wood's lamp. Trichophyton species do NOT fluoresce — Wood's lamp is negative. Coral-red fluorescence is characteristic of Corynebacterium minutissimum (erythrasma).

Bright green fluorescence under Wood's lamp is characteristic of Microsporum species. Trichophyton species are Wood's lamp negative. Coral-red fluorescence indicates erythrasma (Corynebacterium minutissimum), not tinea.

Correct. Extensive tinea not responding to topical terbinafine in India should prompt consideration of terbinafine-resistant T. indotineae. Confirm with KOH, then switch to oral itraconazole 200 mg/day (4–8 weeks for extensive disease). Topical steroid-antifungal combinations must never be prescribed.

India is experiencing an epidemic of chronic, recalcitrant dermatophytosis caused by terbinafine-resistant Trichophyton indotineae. When terbinafine fails, think resistance and switch to oral itraconazole (200 mg/day × 4–8 weeks). Never use topical steroid-antifungal combination creams — they worsen the condition.

The correct answer is to consider terbinafine resistance and switch to oral itraconazole. India has an epidemic of resistant T. indotineae. Topical steroid-antifungal combinations (option A) are particularly harmful — they suppress inflammation and mask the infection while worsening fungal spread.

Correct. Mosaic fungus (cell-wall artefact) is the most common cause of false-positive KOH. The refractile, straight, uniform-width structures crossing cell boundaries are cell junction lines, not hyphae. True hyphae branch irregularly, vary slightly in width, and are confined within keratinocytes.

Mosaic fungus (mosaic artefact) is a common false-positive on KOH: cell wall junctions between squamous epithelial cells appear as linear, refractile, uniform-width structures that cross cell boundaries and run in straight lines. True hyphae are irregular, branch, lie within cells (not crossing boundaries), and show occasional septa.

The description — refractile, uniform width, straight lines crossing cell boundaries — is classic for mosaic fungus artefact, not true hyphae. Real hyphae branch, lie within cells, vary slightly in width, and show septa. Recognising this artefact prevents false-positive diagnoses.

Correct. Onychomycosis requires oral antifungal therapy. Terbinafine 250 mg/day × 12 weeks for toenails is the first-line regimen with the best cure rates. Baseline liver function tests are recommended. Topical agents alone are inadequate for established onychomycosis.

Onychomycosis (tinea unguium) requires systemic therapy; topical agents do not penetrate the nail plate adequately except for very superficial disease. Oral terbinafine 250 mg/day × 12 weeks (toenails) or 6 weeks (fingernails) is standard first-line. Itraconazole pulse (400 mg/day × 1 week/month × 3–4 months) is an alternative. Baseline LFTs are recommended for oral terbinafine.

Onychomycosis requires systemic antifungal therapy — topical creams do not penetrate the nail adequately. Oral terbinafine 250 mg/day × 12 weeks (toenails) is standard first-line. Itraconazole pulse is an alternative. Option D is incorrect — onychomycosis causes morbidity (pain, difficulty walking) and serves as a reservoir for re-infection.

Correct. 'Black dot' tinea capitis = endothrix invasion where hyphae fill the inside of the hair shaft, causing it to break at the scalp surface. T. tonsurans (common in Africa/Americas) and T. violaceum (common in India) are the classical endothrix species.

Endothrix invasion = fungal spores inside the hair shaft; hair breaks at the scalp surface creating the 'black dot' appearance. T. tonsurans and T. violaceum are the commonest endothrix species. Ectothrix = spores on the outside of the hair shaft (Microsporum species). Favus = air spaces (scutula) within the hair.

Black dot pattern = endothrix invasion (spores inside hair shaft) = T. tonsurans or T. violaceum. Microsporum species cause ectothrix invasion (spores on the outside of the hair shaft) with kerion-type inflammatory response and Wood's lamp positivity.

Correct. The widespread misuse of topical steroid-antifungal combinations is the chief driver of India's recalcitrant tinea epidemic. Steroids suppress the immune response, allow fungal proliferation, and alter the clinical appearance (masking the ring). Stop immediately, confirm with KOH, and prescribe appropriate antifungal therapy alone.

Topical steroid-antifungal combination creams are a key driver of the Indian epidemic of recalcitrant tinea. The steroid suppresses the immune response, masking the ring-shaped appearance while allowing fungal spread; the antifungal component is usually at a sub-therapeutic concentration. They must be stopped immediately. The appropriate management is to confirm with KOH and treat with a single-agent antifungal (topical for limited, oral for extensive/recalcitrant disease).

Topical steroid-antifungal combination creams MUST be stopped. The betamethasone suppresses the immune response, worsens fungal spread, and distorts the clinical picture. Continuing or adding more topical agents will not help. The correct approach is to stop the combination cream, confirm with KOH, and treat with antifungal monotherapy — oral for extensive disease.