Pulmonary Fungal Infections 1: Systemic Mycoses Flashcards
What are major themes associated with the pulmonary systemic mycoses?
- Inhaled into lung
- Thermally dimorphic
- NOT PERSON-TO-PERSON TRANSMISSIBLE
- DDx includes TB but Hx points to American dirt NOT FOREIGN CROWDS
- What bugs cause coccidiomycosis?
- Forms?
- Infectious Season?
- Typical scenarios where infection occurs
- Coccidioides immitis
- Mold in soil; Spherule in tisssue
- Summer
- Areas near excavation, southwest US (San Joaquin Valley) and Latin America
What is the infectious component of Coccidioides? What components are noninfectious?
Arthrospores (arthroconidia); Spherules and endospores
What is this? What is important about it?
- Coccidioides spherule
- DIAGNOSTIC OF COCCIDIOMYCOSIS
What are these? What is important about them?
- Coccidioides arthrospores
- Infectious!
What are the majority of presentations of patients with a low to moderate dose of coccidiomycosis?
Betwixt asymptomatic and nonspecific flu-like illness that is self-resolving
Describe pathogenesis of Coccidioides
- Acute Phase: Innate Immunity (Macros) attempt to clear infection (often successful)
- Chronic Phase: Cell Mediated Immunity Required
- IF CMI not intact, patient cannot wall of infection in granulomas and bug can disseminate to bones and meninges (Macrophages as trojan horses)
A patient with Coccidioides infection shows the following rash. What is it? What other Syx can this patient have? Are there bugs in this lesion?
- Erythema Nodosum; No bugs
Fever, arthralgia, erythema multiforme, chest pain
What are risk factors for those who are exposed to a large dose of coccidiomycosis to getting a serious pneumonia or dissemination?
- Advanced Age
- Immunocomp
- Late-stage pregnancy
- Occupational exposure (farmer, construction worker, archaeologist)
- Black/Filipino
What are key findings on exam that point towards coccidioidomycosis?
- Travel/residence in endemic area
- PPD with coccidioidin or spherulin
What must one be conscious of when administering a PPD for coccidioidomycosis?
You will get a + PPD if exposed w/ cleared or contained infection. Negative exam if unexposed or DISSEMINATED (immunocompromised)
Why is observing Erythema Nodosum in a patient with Coccidioidomycosis a good sign?
Infection probably isn’t disseminated
What are important diagnostic tests for coccidioidomycosis infection?
- Spherules on biopsy are diagnostic
- Cutulre on Sabouraud’s agar at 25C (CULTURES ARE INFECTIOUS)
- Serology - positives very reliable (specific) but there are some false negatives
Tx for mild coccidioidomycosis? Persistent infection/dissemination?
- Mild - generally nothing
- Persistent Infection/Dissemination- Amphotericin B and long term Itraconazole (POTENTIALLY YEARS OF TX)
- Meningitis - Fluconazole and potentially intrathecal ampho B
What is the most common systemic mycosis?
Histoplasma capsulatum
What are the two types of asexual spores of Histoplasma?
- Tuberculate macroconidia
- Microconidia
Where is histoplasma normally found? What reproductive processes are histo capable of?
- In acidic damp soil w/ high organic content (Ohio, Missouri, Mississippi) river valleys
- Thermally dimorphic - Mold in soil, yeast in tissue
What would be a possible scenario which leads to infection with histoplasma?
Eating soil, bird or bat droppings, excavation/construction
Describe the pathogenesis of histoplasma
- Inhalation of spores
- Innate immunity can kill low dose but can be overwhelmed by high doses
- Macros engulf spores which may survive endocytosis and lysosomal fusion via bicarb and NH3 production
- Spores -> yeast w/i macros and replicate
- Macros as trojan horses
A patient with histoplasma presents with the following lesion. What does this indicate?
Tongue lesion is a sign of histoplasma dissemination. May indicate immunosuppresion and possible pancytopenia.
What are significant red flags in the exam indicating a person has a Histoplasma infection?
- Acute febrile illness
- Hx: Residence/travel to an endemic river valley; Occupational Exposure (Construction, Birds, Bats)
- Lung Exam: cough, chest pain, hemoptysis, ARDS, cavitary lesions
- Eye Exam: Scars
- PPD: NOT USEFUL
Useful tests for Histoplasma Dx?
- Bloodwork - pancytopenia found in patients w/ disseminated cases
- TWO cultures - Thermally Dimorphic - culture at 25 and 37 C
Tx for Histoplasma infection for mild cases? Pulmonary cases? Disseminated? Meningitis?
- Mild - monitor progress
- Pulm - oral itraconazole 6 - 12 weeks
- Diss - amphotericin B followed by 1 year of itraconazole
- Menin - Fluconazole (penetrates spinal fluid well)
What is the bug that causes Blastomycosis? Where is it found? What for is infectious? Route?
Blastomyces dermatidis; North America in Great Lakes Region in rich wet soil; Conidia by inhalation
