MYCOSES — SUPERFICIAL, CUTANEOUS, SUBCUTANEOUS, SYSTEMIC & OPPORTUNISTIC --- CLASSIFICATION OF MYCOSES Type Depth of Infection Host Response Examples --- --- --
MYCOSES — SUPERFICIAL, CUTANEOUS, SUBCUTANEOUS, SYSTEMIC & OPPORTUNISTIC --- CLASSIFICATION OF MYCOSES Type Depth of Infection Host Response Examples --- --- --- --- Superficial Outermost skin layer only None Pityriasis versicolor, Tinea nigra Cutaneous Skin, hair, nails (keratinized tissue) Cellular immune response Dermatophytoses (ringworm) Subcutaneous Skin + subcutaneous tissue Granulomatous Mycetoma, Sporotrichosis Systemic Deep organs Variable Histoplasmosis, Blastomycosis Opportunistic Any site in immunocompromised host Variable Candidiasis, Cryptococcosis, Aspergillosis --- A. SUPERFICIAL MYCOSES Infection restricted to the outermost horny layer of skin, hair and nails. No cellular response, no pathological changes, purely cosmetic. No discomfort to the patient. Predisposing factors: humidity, immunosuppression, poor hygiene --- 1. Pityriasis Versicolor (Tinea Versicolor) Also called: Dermatomycosis furfuracea, Tinea flava Causative agents: Malassezia globosa and Malassezia furfur - These are lipophilic yeasts (feed on skin oils/lipids) - Part of normal skin flora — only become pathogenic under warm, humid conditions Clinical features: - Hypopigmented or hyperpigmented skin patches - Usually on trunk, back, underarm - Occasionally on face Diagnosis: - KOH mount of skin scales → "spaghetti and meatballs" appearance (short curved septate hyphae + budding yeast cells) - Under Wood's lamp → fluoresces yellow - Culture media must be supplemented with fatty acids (lipophilic organism) Treatment: Topical imidazole --- 2. Tinea Nigra - Dark, non-scaly patches on palms - Caused by Hortaea werneckii (dematiaceous/dark fungus) - Diagnosis: KOH mount showing dark septate hyphae - Treatment: Topical azoles or salicylic acid 3. Black Piedra - Hard dark nodules on hair shafts - Caused by Piedraia hortae - Treatment: Shaving affected hair + topical azoles 4. White Piedra - Soft white/cream nodules on hair shafts - Caused by Trichosporon spp. - Treatment: Shaving affected hair + topical azoles --- B. CUTANEOUS MYCOSES (DERMATOPHYTOSES) Involves skin, nails and hair infections. Caused by fungi that invade superficial keratinized tissue . Clinical manifestation = ringworm/tinea . Evoke cellular immune response and may cause hypersensitivity (id reaction). --- Causative Agents — Dermatophytes Dermatophytes are keratinophilic (keratin-loving). They use keratin as nitrogen source and produce keratinases (extracellular enzymes that hydrolyze keratin). Three genera: Genus Sites Infected Age Group Macroconidia Microconidia --- --- --- --- --- Microsporum Hair, skin; rarely nails Children mainly Numerous, thick-walled, rough, spindle-shaped Rare Trichophyton Hair, skin AND nails Both children & adults Rare, thin-walled, smooth, pencil-shaped Abundant Epidermophyton Skin, nails; rarely hair Adults mainly Numerous, smooth, club-shaped in clusters Absent --- Ecology — Sources of Dermatophytes Type Source Transmission Examples --- --- --- --- Anthropophilic Humans only Man to man by close contact or contaminated objects (comb, hat) T. rubrum , E. floccosum , M. audouinii Zoophilic Animals Close contact with animals (cats, dogs, cows) or contaminated products M. canis , M. nanum , T. verrucosum Geophilic Soil Direct exposure to soil M. gypseum --- Clinical Forms of Dermatophytosis Spread peripherally from foci to produce ring-like lesions — hence "ringworm" or "tinea." Named by site affected: Tinea Pedis (Athlete's Foot) - Most prevalent of all dermatophytoses - Caused by T. rubrum , T. mentagrophytes , E. floccosum (anthropophilic) - Starts itchy between toes → small vesicles rupture → skin macerated, peels, cracks - Prone to secondary bacterial infection → lymphangitis and lymphadenitis Tinea Corporis (Ringworm of the Body) - Also called Tinea circinata, Tinea glabrosa - Infection of glabrous (hairless) skin - Annular lesions with active border — may be pustular or vesicular - Caused by T. rubrum , T. mentagrophytes , M. canis , E. floccosum - Often from a pet or another body site - Usually resolves in several months - Treatment: topical ketoconazole, miconazole Tinea Capitis — scalp and hair; mainly children Tinea Barbae — beard area Tinea Cruris (Jock Itch) — groin area Tinea Unguium (Onychomycosis) — nails Tinea Manum — hands Tinea Faciei — face Tinea Imbricata — concentric ring pattern; tropical regions --- Laboratory Diagnosis of Dermatophytoses Specimen collection: - Skin scales, nail scrapings, hair clippings - Scrape outwards from the edge of lesion with scalpel - Stop antifungals one week before nail specimen collection 1. Wood's Lamp (Macroscopic) - Infected hair/scalp lesions fluoresce under UV light - Microsporum spp. fluoresce bright green - Trichophyton spp. generally do NOT fluoresce 2. Direct Microscopy — KOH Mount (10–20% KOH) - KOH digests protein debris and dissolves keratin, leaving fungal elements visible - DMSO can be added to hasten clearing - In skin/nails → branching hyphae or chains of arthrospores seen - In hair → hyphae or spores detected: - Ectothrix — spores OUTSIDE the hair shaft - Endothrix — spores INSIDE the hair shaft 3. Calcofluor White (CFW) - Fluorescent stain — binds specifically to glucan and chitin in fungal cell wall - Emits blue fluorescence under illumination - Excellent morphology of pathogenic fungi 4. Culture - Sabouraud Dextrose Agar (SDA) containing: - Actidione (cycloheximide) — inhibits saprophytes - Chloramphenicol — inhibits bacteria - Incubated at room temperature for up to 4 weeks - Colonies identified by morphology, colour, texture - Microscopic examination using Lactophenol Cotton Blue (LPCB) stain: - Lactic acid — preserves fungal structure - Phenol — kills live organisms - Glycerol — prevents drying - Cotton blue — imparts blue colour to structures --- Treatment of Dermatophytoses Topical: - Non-specific: Whitfield's ointment - Specific: azole creams/lotions/shampoos — clotrimazole, ketoconazole, miconazole Oral (for nail, scalp, severe skin infections): - Griseofulvin, terbinafine, itraconazole Prevention: proper hygiene, sterilization of instruments with hot mineral oil, effective treatment of cases, reduce contact with infectious materials --- C. SUBCUTANEOUS MYCOSES Chronic, localized infections of skin and subcutaneous tissue following traumatic implantation of the fungus (e.g. thorn prick, splinter). All causative fungi are soil saprophytes . Infection evolves slowly as the fungus adapts to host tissue. Difficult to treat — surgical intervention (excision or amputation) frequently required. --- 1. Mycetoma (Madura Foot) Mycotic infection of humans and animals caused by different fungi and actinomycetes. Two types: - Eumycotic mycetoma — caused by true fungi - Actinomycotic mycetoma — caused by Actinomycetes (bacteria-like organisms) Distribution: Worldwide but most common in barefoot populations in tropical/subtropical regions. Endemic in Africa, India, Central and South America. Mainly affects feet — mycetoma pedis (Madura foot) Clinical features: - Involves cutaneous and subcutaneous tissue; may reach bone - Enters through wounds on feet, hands or back - Starts as small hard painless nodule → softens → ulcerates → discharges viscous purulent fluid containing granules - Granule characteristics (colour, size, hardness) depend on causative organism: - Yellow granules → actinomycetes - Black granules → fungi (e.g. Madurella mycetomatis ) - White granules → fungi (e.g. Pseudallesceria boydii ) Causative Agents: Actinomycotic Eumycotic --- --- Nocardia asteroides , N. brasilensis , N. caviae Madurella mycetomatis , M. grisea Actinomadura madurae , A. pelletieri Pseudallesceria boydii Actinomyces israelii Exophiala jeanselmei , Phialophora verrucosa Laboratory Diagnosis: 1. Specimen: tissue biopsy, serosanguinous fluid with granules 2. Macroscopic exam of granules: yellow (actinomycetes) vs black/white (fungi) 3. Microscopy: KOH + calcofluor white; H&E staining shows true septate hyphae in eumycotic type 4. Cu