DR7.1-2 | Fungal Infections — Glossary

The raised, advancing, scaly edge of an annular dermatophyte lesion where viable fungus is concentrated; the correct site to scrape for a KOH mount, as the centre often gives false negatives.

Rounded or oval yeast cells reproducing by budding; seen with pseudohyphae in Candida infections on KOH microscopy.

A yeast (commonly Candida albicans) causing cutaneous and mucosal candidiasis; on KOH mount shows pseudohyphae together with budding yeast cells.

Infection by Candida (commonly C. albicans) of skin folds or mucosae, showing beefy-red erythema with satellite pustules or white mucosal plaques; KOH shows pseudohyphae with budding yeast.

The structural polysaccharide of the fungal cell wall that resists alkaline (KOH) digestion, allowing fungal elements to remain visible while human keratin is cleared.

A keratin-digesting fungus of the genera Trichophyton, Microsporum, or Epidermophyton that causes tinea (ringworm); shows long, branching, septate hyphae on KOH mount.

Infection of keratinised tissue (skin, hair, nail) by dermatophyte fungi (Trichophyton, Microsporum, Epidermophyton), named by site; the commonest superficial fungal infection in India.

The commonest pattern of nail dermatophytosis, with infection entering at the distal/lateral nail edge causing subungual hyperkeratosis and onycholysis.

A triazole antifungal (CYP51 inhibitor) used primarily for candidal infections and for some dermatophyte and pityriasis versicolor indications.

Growth of a fungal sample on selective media (e.g. Sabouraud's dextrose agar) for species identification and, where available, sensitivity testing; used for recalcitrant tinea and where terbinafine resistance is suspected.

A fungistatic antifungal that disrupts fungal microtubules; classic first-line systemic agent for tinea capitis in children, particularly for Microsporum infection.

A triazole antifungal inhibiting lanosterol 14-α-demethylase (CYP51), active against dermatophytes, Candida, and Malassezia; now the commonly used agent for recalcitrant terbinafine-resistant tinea in India.

A bedside microscopy test in which a skin, nail, or hair sample is mounted in potassium hydroxide solution to clear keratin and reveal fungal elements; the first-line confirmatory test for superficial fungal infection.

The lipophilic yeast causing pityriasis (tinea) versicolor; on KOH mount shows short curved hyphae mixed with clusters of round spores — the "spaghetti and meatballs" appearance.

A false-positive KOH finding — a refractile, geometric, non-branching network of cholesterol/cell-wall debris outlining corneocyte borders, to be distinguished from true uniform branching hyphae.

Superficial infection by the yeast Malassezia furfur producing hypopigmented or hyperpigmented finely scaly macules on the trunk; KOH shows the 'spaghetti and meatballs' pattern.

A strong alkali (used at 10–20%) that digests human keratin and cellular debris while sparing the chitinous fungal cell wall, clearing the background so fungal hyphae and yeasts become visible.

Chains of elongated yeast cells constricted at their junctions, characteristic (with budding yeast) of Candida on KOH mount; not true uniform septate hyphae.

Filamentous fungal growth divided by regular cross-walls (septa); long, branching septate hyphae on KOH are the hallmark of dermatophyte infection.

The classic KOH mount description of pityriasis versicolor: short curved hyphae (spaghetti) intermixed with clustered round yeast spores (meatballs).

The fungal enzyme targeted by allylamines such as terbinafine; mutations in its gene reduce drug binding and produce terbinafine resistance.

The outermost keratin-rich layer of the epidermis composed of dead corneocytes; the layer colonised by dermatophytes and dissolved by KOH during slide preparation.

An allylamine antifungal that inhibits squalene epoxidase; first-line oral agent for dermatophytosis, but now frequently undermined by resistance in India.

Reduced clinical response to terbinafine in dermatophytosis due to squalene epoxidase (SQLE) gene mutations (notably in the T. mentagrophytes/indotineae complex); a major cause of chronic recurrent tinea in India, managed by switching to itraconazole.

Dermatophyte infection of keratinised tissue, named by site: corporis (body), cruris (groin), pedis (foot), capitis (scalp), unguium (nail).

Dermatophyte infection of the scalp and hair, mainly in children, presenting with scaly patches and broken hair stubs; requires mandatory systemic antifungal therapy.

Dermatophyte infection of the trunk or limbs, classically an annular scaly plaque with a raised active margin and central clearing.

Dermatophyte infection of the groin and inner thighs, presenting as itchy erythematous scaly plaques, often with satellite lesions; favoured by heat and humidity.

Dermatophytosis with atypical, modified morphology (loss of the sharp active border, wider spread) caused by prior topical corticosteroid use, often combined in OTC creams.

Dermatophyte infection of the foot, presenting as toe-web maceration and fissuring or diffuse 'moccasin' scaling of the soles.

Dermatophyte infection of the nail producing thickening, discolouration, crumbling, and subungual debris; sampled by scraping subungual debris for KOH.

A long-wave ultraviolet (UVA) lamp used as a diagnostic adjunct; in tinea capitis it produces green fluorescence with Microsporum species but NOT with Trichophyton (the predominant Indian cause).