Week 4: Mycoses

Question 1

General features of systemic mycoses

Answer 1

• -cause infection in both normal and immunocompromised hosts
• endemic pathogens
• dimorphic fungi
• thermal dimorphism: mold in room temperature, yeast in body temperature 37degrees
• acquired by inhalation

Question 2

Coccidioidomycosis

Answer 2

• etiology: coccidioides immitis
• from soil and dust
• southwestern US, N. mexico, central and south america
• white fluffy mold in soil and culture, reproduces by arthroconidia

Question 3

Clinical finding in coccidioidomycosis

Answer 3

1. primary pulmonary cocci
   - mostly asymptomatic
   - self-limited pneumonia: non productive cough, fever, night sweats, anorexia
2. San Joaquin valley fever
   - immune complex formation
   - rash, erythema nodosum, erythema multiform
   - arthritis
3. Progressive pneumonia
4. disseminated cocci
   - ~1% patients: skin-cold abscesses, bone/joint, meninges

Question 4

Risk factors for dissemination of coccidioidomycosis

Answer 4

• age extremes
• male
• genetics: filipino>AA>native americans>asian
• Pregnancy
• depressed cell mediated immunity
• serum CF titer >1:32

Question 5

Diagnosis and Rx of Coccidioides immitis

Answer 5

-complement fixation test
-culture of sputum, blood
-pathology
-not skin test
RX
-fluconazole, itraconazole: preferred (interferes with ergosterol synthesis, cell membrane component)
-amphotericin B

Question 6

Histoplasmosis

Answer 6

• etiology: histoplasma capsulatum
• ecology: moist surface soil, with droppings of birds and bats
• worldwide, in US: mississippi and ohio river valleys
• White fluffy mode, reproduces by arthroconidia
• pathogenic mechanisms: survives in unstimulated macrophages and disseminates within monocytes, cell mediated immune response causes granulomas

Question 7

Clinical features of histoplasmosis

Answer 7

• Asymptomatic in 90%
• symptomatic with heavy exposure
• primary acute: fever, non productive cough, headache, myalgias, arthralgias
• 90% recover spontaneously
• residual calcified lesions

Question 8

Sequelae, dissemination, and progressive histoplasmosis

Answer 8

1. inflammatory sequelae: arthritis, pericarditis
2. disseminated histoplasmosis: fever, weight loss, fatigue, oropharyngeal ulcers, hepatosplenomegaly, bone marrow involvement
3. progressive
   - lung destruction, cavities, fibrosis
   - mediastinal fibrosis: not stopped or slowed by anti fungal therapy or corticosteroids

Question 9

Dx and Rx of histoplasmosis

Answer 9

Dx: culture, pathology, serology of blood and urine
Rx: itraconazole is drug of choice. Amphotericin B

Question 10

Blastomycosis

Answer 10

• etiology: blastomyces dermatitidis
• ecology: decaying organic matter
• geography: N. america (Ohio/Mississippi river valleys, great lakes, south east), africa
• no capsule, thick walled yeast
• pathogenic mechanisms: shed immunodominant Ag from cell surface, modify cell wall composition

Question 11

Clinical features of blastomycosis

Answer 11

1. Acute blastomycosis
   - fever, arthralgias, myagias, headahce
   - productive cough, pleuritic chest pain
   - erythema nodosa
   - resolves spontaneously
2. Chronic
   - chronic pulmonary
   - cutaneous blastomycosis

Question 12

Aspergillus

Answer 12

• common mold found in environment
• septated hyphae, hyphae branch at acute angle (45 degrees)
• most common: aspergillus fumigatus
• risk factors: immunocompromised, hematologic malignancy, pulmonary disease, environmental conditions

Question 13

Aspergillus clinical syndromes

Answer 13

1. allergic bronchopulmonary aspergillosis
   - allergic response characterized by transient pulmonary infiltrates
   - asthma, central bronchiectasis, elevated IgE, eosinophilia, serum precipitating antibodies to A. fumigatus
2. fungus ball-aspergilloma
   - solid mass of hyphae growing in previously existing pulmonary cavity
   - usually asymptomatic, but hemoptysis may occur
   - rx with surgical resection
3. invasive disease: pulmonary
   - immunosuppressed
   - fever, progressive dry cough, dyspnea, pulmonary infiltrates
   - Halo sign, air crescent sign
4. invasive disease: disseminated
   - brain, bone cutaneous
   - Rx: voriconazole