41 - Fungal Diseases

mycosis

fungal infection that overcomes host defenses

• entry points → lungs, skin, GI tract, blood vessels, paranasal sinuses

  • most infections start in the lungs

• adaptation and propagation due to specific enzymes and morphological changes

• host factors play a role in dissemination

• classifications:

  • superficial (cutaneous) → limited to outermost layers of hair and skin, do not invade living tissues

    • Microsporum, Trichophyton, Epidermophyton

    • diseases with “tinea”

  • subcutaneous → involves dermis, subcutaneous tissues, muscle, and fascia

    • enter via trauma

    • Sporotrichosis, Chromoblastomycosis, Mycotic mycetoma

  • systemic (primary pathogens) → originate in lungs and spread to other organ systems

    • Paracoccidiodomycosis

  • systemic (opportunistic pathogens) → immunocompromised states

    • Candidiasis, Cryptococcosis, Aspergillosis

cutaneous mycoses

affect skin, hair, and nails; do not invade deeper tissues

• fungi — dermatophytes that produce keratinases to allow for penetration, not dimorphic

  • Microsporum, Trichophyton, Epidermophyton

• tinea = “ringworm” → lesions of skin or scalp

  • tinea corporis → small lesions occuring anywhere on body

  • tinea pedis → “athlete’s foot”, infection of toe webs and soles

  • tinea cruris → “jock itch”; infection of groin, perineum, or perianal area

  • tinea barbae → infection of bearded areas of face and neck

  • tinea nigra → causes dark brown to black painless patches on soles of hands and feet

  • tinea versicolor → blotchy discoloration of skin

subcutaneous mycoses

involves dermis, subcutaneous tissues, muscle, and fascia

• known as “rose gardener’s disease”

• disease — sporotichosis

• fungi — Sporothrix schenkii

  • dimorphic, round, or cigar-shaped budding yeasts observed in budding yeasts

• entry — trauma

• symptoms — local pustules or ulcers with nodules seen along lymphatic system

  • linear spread up arm

• treatment — oral KI, amphotericin B, or itraconazole

• prevention — avoid touching plants, moss, or wood

systemic mycoses

• fungi — dimorphic

• entry — lungs and may spread to organ systems

• symptoms — asymptomatic and self-limited

• disease — based on organism

  • coccidioidomhycosis → Coccidioides immitis

  • histoplasmosis → Histoplasma capsulatum

  • blastomycosis → Blastomyces dermatidis

  • paracoccidioidomycoses → Paracoccidioides brasilensis

coccidioiomycosis

systemic mycoses known as “valley fever”

• fungi — Coccidioides immitis

  • dimorphic fungus

  • develops into spherules that are filled with endospores in tissue, existing as mold in soil

• geographical niche — Southwestern US (California), northern Mexico

• infection — lungs, with potential dissemination to CNS, skin, and joints

  • causes pneumonia, possible meningitis

• symptoms — anorexia, weight loss, cough, hemoptysis

  • 10% of people develop erythema nodusum (inflammation causing red nodules on skin) due to hypersensitivity of antigens

• diagnosis — high titers of antibodies in disseminated disease

• virulence factors — dimorphism, ineffective TH2 response, urease production, extracellular proteases

• treatment — amphotericin B, ketoconazole, fluconazole, itraconazole

histoplasmosis

systemic mycoses

• fungi — Histoplasma capsulatum

  • dimorphic fungus

  • found in bird and bat droppings

• infection — reticuloendothelial system

  • manifests in bone marrow, lungs, liver, and spleen

  • adults → pulmonary disease; children → hepatosplenomegaly

• diagnosis — uninucleate budding cells seen residing in macrophages

• virulence factors — dimorphism, modulation of pH in phagosome, iron and calcium uptake

• treatment — ketoconazole, fluconazole, itraconazole

blastomycosis

systemic mycoses

• fungi — Blastomyces dermatitidis

  • dimorphic fungus

  • yeast is round with single broad-based bud

  • found in soil containing organic debris (rotting wood, animal droppings, plant material)

• infection — most often lungs and skin, can also affect bone and urogenital tract

  • causes chronic granulomatous disease

  • disseminated disease results in ulcerated granulomas

• virulence factors — dimorphism, ineffective TH2 response

• treatment — amphotericin B, ketoconazole, oral itraconazole, surgical excision of granulomas

paracoccidioidomycosis

systemic mycoses

• fungi — Paracoccidioides brasiliensis

  • dimorphic fungus

  • budding yeast with “captain’s wheel” formation

• geographical niche — middle of Mexico to Central and South America

• infection — mucous membranes, skin, pulmonary system

  • causes chronic granulomatous disease

• virulence factors — dimorphism, intracellular survival, ineffective TH2 response, hormonal influences

• treatment — ketoconazole, sulfonamides, amphotericin B

mucormycosis

systemic mycoses due to opportunistic pathogen

• fungi — Mucor, Rhizopus, Absidia, Cunninghamella species

• infection — sinuses, brain, lungs

• risk factors — leukemia, steroid treatment, diabetes, other immunocompromised conditions

• diagnosis — irregular hyphae in clinical specimen

• treatment — amphotericin, surgical debridement

candidiasis

systemic mycoses due to opportunistic pathogen

• fungi — Candida albicans

• infection — oropharyngeal, esophagitis, vulvovaginal, superficial of skin and nails, pneumonia, endocarditis and pericarditis, hematogenous, ocular, bone and joint, CNS

• diagnosis — germ tubes and pseudohyphae

• immunity — humoral and cell-mediated

  • increased vaginal candidiasis in AIDS patients due to decreased cell-mediated immunity

• treatment —

  • local infection → oral or topical clotrimazole or nystatin

  • mucocutaneous → ketoconazole

  • disseminated → amphotericin B ± flucytosien or ketoconazole

aspergillosis

systemic mycoses due to opportunistic pathogen

• fungi — Aspergillus fumigatus

  • exists only as mold

  • characteristic V-shaped dichotomous branches → large branching septate hyphae

  • infection by airborne conidia

• infection — wounds, cornea, lungs

• symptoms — allergic disease, hemoptysis, granulomas

• treatment — amphotericin B, itraconazole, surgery

cryptococcosis

systemic mycoses due to opportunistic pathogen

• fungi — Cryptococcus neoformans

  • oval budding yeast with wide capsule

  • found in pigeon droppings

• infection — lung dissemination to CNS

• symptoms — meningitis

• diagnosis — spinal fluid with India ink

• treatment — amphotericin, flucytosine, fluconazole in AIDS patients