Mycology: Subcutaneous, Cutaneous, and Superficial Mycoses

Vocabulary flashcards covering the clinical manifestations, microscopic morphology, culture characteristics, and causative agents of subcutaneous, cutaneous, and superficial mycoses.

Sporotrichosis

A chronic subcutaneous fungal infection (also known as Rose gardener disease) caused by Sporothrix schenkii, presenting with nodules that ulcerate and necrose along lymphatic channels, and thermal dimorphism at $25\,^\circ\text{C}$ and $37\,^\circ\text{C}$.

Sporothrix schenkii

A thermally dimorphic soil fungus that enters through wounds, forming septate hyphae with rosette-like conidia clusters at $25\,^\circ\text{C}$ and round or cigar-shaped yeast cells at $37\,^\circ\text{C}$.

Asteroid body

A non-specific host tissue response seen around yeast cells upon direct KOH examination with methenamine silver stain in sporotrichosis.

Chromoblastomycosis

A chronic subcutaneous infection caused by soil-dwelling dematiaceous fungi (Fonsecaea, Phialophora, Cladosporium), producing verrucous, cauliflower-like lesions on the lower extremities.

Copper penny bodies

Sclerotic fungal bodies produced in tissue by all causative agents of chromoblastomycosis.

Eumycotic mycetoma

A form of mycetoma—a chronic subcutaneous infection with painless, swollen granulomatous lesions and sinus tracts—specifically caused by fungi.

Actinomycotic mycetoma

A form of mycetoma—a chronic subcutaneous infection with painless, swollen granulomatous lesions and sinus tracts—specifically caused by bacteria.

Rhinosporidiosis

A chronic infection in divers caused by Rhinosporidium seeberi, characterized by polypoid masses and seropurulent discharge in the nasal mucosa, conjunctiva, genitalia, or rectum.

Rhinosporidium seeberi

The causative agent of rhinosporidiosis with a natural reservoir in fish and aquatic insects; it displays spherules with endospores microscopically and cannot be cultured in vitro on artificial media.

Microsporum

A genus of dermatophytes infecting skin and hair, characterized by large, thick-walled, multi-septate, canoe-shaped/fusiform macroconidia directly from hyphae and fluorescence under a Wood lamp.

Microsporum canis

A species of Microsporum capable of growth on polished rice grains.

Epidermophyton floccosum

A dermatophyte species that infects skin and nails, forming clavate, smooth-walled macroconidia and thick-walled chlamydoconidia, while lacking microconidia.

Trichophyton

A genus of dermatophytes infecting skin, nails, and hair, producing smooth, thick-walled, elongate, cigar-shaped macroconidia and oval microconidia singly or in grape-like clusters.

Trichophyton rubrum

A Trichophyton species featuring tear drop-shaped microconidia attached to hyphae ('birds on a wire'), producing red pigment on cornmeal agar and utilizing sucrose.

Trichophyton mentagrophytes

A Trichophyton species that tests positive for urea and forms wedge-shaped perforations in the hair perforation test.

Pityriasis versicolor

A superficial mycosis caused by Malassezia furfur, characterized by hypo- or hyperpigmented, scaly, itchy lesions on the trunk and upper arms.

Malassezia furfur

A lipophilic fungus requiring oil added to the agar surface for culture, causing pityriasis versicolor.

"Spaghetti and meatballs"

The microscopic pattern of Pityriasis versicolor consisting of clusters of single budding round/bottle-shaped yeast cells alongside short, unbranched, hyaline hyphae.

Tinea nigra

A chronic, rare superficial fungal infection caused by Hortae (Exophiala) werneckii, presenting as a single, black spot with a distinct border and slight itching.

Hortae werneckii

The causative agent of tinea nigra, possessing brown, septate, branching hyphae and yeast-like conidia with distinct intra-cellular divisions.

White piedra

A common superficial hair shaft infection caused by Trichosporon beigelii, featuring white to tan nodules loosely adhering to the hair shaft.

Trichosporon beigelii

The causative agent of white piedra (also known as T. cutaneum), producing crushed nodules with round/rectangular arthroconidia and blastoconidia.

Black piedra

A superficial hair shaft infection in tropical regions caused by Piedraia hortae, characterized by hard black nodules tightly adhered to the hair shaft.

Piedraia hortae

The causative agent of black piedra whose ascospore sexual state causes infection, forming asci containing $2\text{ to }8$ ascospores within cavities of infected hair.