Superficial Skin Mycosis and Cutaneous Infections

Vocabulary flashcards covering superficial fungal, bacterial, and parasitic skin infections, their causal organisms, microscopic features, and key clinical manifestations based on the lecture notes.

Dermatophytes

Monomorphic, saprophytic fungi with septate, filamentous hyphae that require keratin for growth, produce keratinases, cannot grow at $37^\circ\text{C}$, and cause slow-expanding annular lesions with raised scaly borders.

Trichophyton spp.

A genus of dermatophytes characterized microscopically by abundant single, spherical, pyriform, or clavate microconidia and small numbers of thin-walled, smooth, multiseptated, pencil-shaped macroconidia.

Microsporum spp.

A genus of dermatophytes characterized microscopically by single, smooth-walled microconidia and multiseptated, thick, rough-walled, fusiform (spindle-shaped) macroconidia.

Epidermophyton spp.

A genus of dermatophytes that produces no microconidia and is characterized by multiseptated, thin, smooth-walled macroconidia with a 'beaver tail' appearance.

Anthropophilic

Refers to dermatophyte species whose route of transmission occurs primarily from human to human through direct contact or fomites.

Zoophilic

Refers to dermatophyte species whose route of transmission occurs from infected animals to humans.

Geophilic

Refers to dermatophyte species whose route of transmission occurs from soil or plants to humans.

Melanin (Fungal Virulence Factor)

A high molecular weight dark brown or black pigment located in the fungal cell wall that protects against UV damage, enzymatic lysis, temperature extremes, and decreases phagocytosis.

Tinea versicolor

A localized, slowly progressing superficial fungal infection caused by Malassezia spp., characterized by hypopigmented or hyperpigmented confluent plaques with fine scales in seborrheic areas.

Malassezia furfur

A lipophilic, dimorphic yeast that lacks the FAS gene, forms part of normal skin flora in lipid-rich areas, and displays a 'spaghetti and meatballs' appearance (short hyphae and spores) on microscopy.

Tinea nigra

A localized, slowly progressing superficial fungal infection caused by Hortae werneckii, presenting as flat, painless, non-itchy, light brown to black patches on the palms or soles.

Hortae werneckii

A dematiaceous fungus transmitted via contact with soil, wood, or vegetation through skin abrasions, causing Tinea nigra and showing pigmented hyphae in skin scrapings.

Sporothrix schenckii

A thermally dimorphic fungus causing subcutaneous sporotrichosis, displaying a 'flowerette' form in the mold phase and sparse cigar-shaped yeasts in tissue specimens.

Cutaneous larva migrans

An intensely itchy, acute parasitic skin eruption caused by migrating hookworm larvae, characterized by elevated, serpiginous ('snake-like') tracks approximately $3\,\text{mm}$ in diameter.

Ancylostoma braziliense

A common species of hookworm whose filariform larvae (L3) penetrate human skin using proteases and lipases, causing zoonotic cutaneous larva migrans before dying within 5 to 6 weeks.

Erythrasma

A localized, slowly spreading bacterial skin infection of intertriginous areas caused by Corynebacterium minutissimum, which fluoresces coral-red under UV light (Wood's lamp).

Corynebacterium minutissimum

A Gram-positive bacillus causing erythrasma in warm, moist skin folds; it produces porphyrins during heme metabolism, which fluoresce coral-red under a Wood's lamp.