Fungal Infections

Question 1

Pneumocystis jiroveci Pneumonia

Answer 1

• Inhaled, common in AIDS patients (probably latent endogenous infection), often fatal.
• Trophozoites (yeast-like) reproduce in alveolar type 1 cells and form cysts and rupture - alveoli fill with frothy eosinophillic material; diffuse lung inflitrate.
• Best seen with methenamine silver stains

Question 2

Candida (albicans)

Answer 2

• Usually superficial (deep infections uncommon and life threatening)
• Endogenous flora, most common precipitating factor = antibiotic use. Yeast converts to invasive hyphae or pseudohyphae form.
• Limited to mucocutaneous sites:
  
  • Thrush = oral cavity, fuzzy white coat on tongue (maceration predisposes)
  • Vulvovaginitis = thick white discharge, itchy (antibiotics, preg., diabetes, steroids)
  • Sepsis and disseminated candidiasis = usually deadly (catheter, IV, dialysis)
  • Endocarditis = large vegetations (IV drug use)
  • Other surfaces include esophagitis, paronychia (nailbeds), diaper rash and intertrigo (opposed skin surfaces)

Question 3

Aspergillosis

Answer 3

-spores (conidia) inhaled
-Allergic bronchopulmonary aspergillosis: restricted to
asthmatics, spores can germinate in airways and cause long-term antigen exposure → exacerbation and infiltrates
-Aspergilloma (fungus ball): Occur in old TB cavities. Cavity wall is collagenous connective tissue with lymphs and plasma cells. Usually left untreated if asymptomatic.
-Inasive Aspergillosis: Occurs when neutrophil count is low (steroids, leukemia). Produces lung and pleural infarcts, but often spreads to blood and causes disseminated infec tion and thrombosis. Usually fatal, antifungals may help.

Question 4

Mucormycosis (Zygomycosis)

Answer 4

• Environmental fungi, cause severe necrotizing, invasive infections that begin in sinuses and lungs (spores are inhaled)
• Rhinocerebral: creates a black crust with friable/hemorrhagic underlying tissue - spreads to vessels and brain. Tx = surgery, amphotericin B, may be fatal
• Pulmonary: Usually fatal, looks like aspergillosis (sepsis and infarction)
• Subcutaneous zygomycosis: In the tropics, hard inflamm. mass (infects subcutaneous fat) on shoulder, trunk, buttock, thigh

Question 5

Cryptococcosis (C. neoformans) - encapsulated

Answer 5

• Inhaled- natural reservoir is pigeon droppings
• Impaired cell-mediated immunity common (AIDS, hodkins disease, leukemia)
• CNS = site of primary infection–meningitis. Also causes progressive pulmonary disease
• Fatal without treatment
• Proteoglycan capsule is critical for virulence, - stains poorly with H&E - stains with mucicarmine
• India Ink stain of CNS infection

Question 6

Histoplasmosis

Answer 6

• Histoplasma capsulatum.
• Primarily effects lung, typically SELF_LIMITED in HEALTHY.
• Intracellular, macrophages = > granulomatous, may resemble TB. => caseous necrosis + calcifications.
• Can dissemminate bone, spleen, liver, adrenal glands, mucocutaneous membranes–AIDS, hepatosplenomegaly (granulomatous deposits) immunocompromised–fatal,

Question 7

Coccidioidomycosis “Valley fever” “Desert Fever”

Answer 7

• “Valley fever” “Desert Fever”
• Coccidioides immitis or Coccidioides posadasii
• Endemic in certain parts of Arizona, California, Nevada, New Mexico, Texas, Utah.
• Flu-like, maculopapular rash,
• Begins with pulmonary infection (granuloma-caseous)–nodules form in lung with hemoptysis, then disseminates, can cause meningitis in immunocompromised.
• usually after pulomary infection, appearance of eryhthema nodosum (IgG deposits-allergic reaction in fat underneath skin)

Question 8

Blastomycosis (Blastomyces dermatitidis)

Answer 8

• Very similar to coccidiomycosis, granulomatous, but also suppurative pulmonary dissease–cavitary pneumonia and meningitis with cerebral abscesses.
• Endemic to Midwest, Mississippi river and Ohio river basins, and around the Great Lakes.
• Skin (>50%) and bones (>10%) are most common sites of extrapulmonary involvement.
  
  • skin lesions from disseminated infection resembling squamous cell carcinoma.
• Usually self-limited (1/3 of patients)

Question 9

Paracoccidioidomycosis (South American/Brazilian Blastomycosis)

Answer 9

• similar to coccidiodomycosis + blastomycosis
• chronic granulomatous infection (with purulent exudates) starting with lung involvement–dissemination in immunocompromised to skin, oropharynx, adrenals, and macrophages of lymphatic system.
• central + south america
• usually acute, self-limited and mild disease

Question 10

Sporotrichosis

Answer 10

• Rose Gardner’s disease
  
  • accidental inoculation through breaks in skin from thorns piercing skin.
• chronic granulomatous skin infection with suppurative center-necrosis and ulceration–lead to secondary cellulitis
• can disseminate through lymphatic vessels-spread to joints and bone.

Question 11

Chromomycosis

Answer 11

• tropics and subtropics
• barefooted agricultural workers
• inoculation through skin–lesion(papule) and become verrucous (wart like with ulceration)

Question 12

Dermatophyte Infections (Microsporum, Epidermophyton and Trichophyton)

Answer 12

• obtain nutrients from keratin–common and benign
• Athlete’s foot or tinea pedis
• Ringworm of the body or tinea corpora
• Facial ringworm or tinea faciei
• Blackdot ringworm or tinea capitis
• Scalp ringworm or tinea capitis
• Ringworm of the hands or tinea manuum
• Ringworm of the nail, Onychomycosis, or tinea unguium

Question 13

Mycetoma

Answer 13

• chronic granulomatic + suppurative cutaneous disease-through breaks in the skin
• tropical workers–affect feet: MADURA FOOT
  
  • disfiguring skin infection–abscesses that combine–large abscesses with ulceration–purulent discharge-white or black.