PBL #5 Flashcards
1
Q
What are the causes of pulmonary nodules?
A
-
Malignant neoplasms:
- non-small cell lung cancer, Small cell carcinoma, Solitary metastasis, Primary pulmonary lymphoma, Primary pulmonary carcinoid, Malignant teratoma, Pulmonary blastoma
-
Benign neoplasms:
- Hamartoma, Chondroma, Hemangioma, Arteriovenous malformation, Fibroma, Neural tumor, Sclerosing hemangioma
-
Infections:
- Granulomatous infections: T, histoplasmosis, coccidioidomycosis, blastomycosis, cryptococcosis, pulmonary aspergilloma
- Bacterial infection: nocardiosis, antinomycosis, round pneumonia
- Measles
- Septic emboli
- Abscess
- Congenital causes: bronchogenic cyst, bronchial atresia w/ mucoid impaction, sequestration
- Other stuff: amyloid, sarcoidosis, RA, granulomatosis with polyangiitis
2
Q
What is the prevalence of pulmonary nodules?
A
- Solitary pulmonary nodule found on up to 0.2% of all chest films
- Lung nodules found on up to 50% of all lung CT scans
3
Q
What is the significance of calcification and cavitation of a pulmonary nodule?
A
- Calcification:
- Usually indicates a benign disease.
- Benign patterns of calcification: central nidus, laminated, diffuse, popcorn.
- If it has 1 of these 4 patterns and is < 3 cm, it is most likely benign.
- Cavitation:
- gas-filled area on the lung in the center of a nodule or area of consolidation (lung tissue filled with water)produced by the expulsion of a necrotic part of a lesion
- Noninfectious disease associations: Malignancy, granulomatosis with polyangiitis (Wegener’s), pulmonary infarct due to embolism.
- Infectious associations: Necrotizing pneumonias and lung abscesses, Mycobacterium tuberculosis, Fungal infections, septic emboli.
4
Q
What are the organisms responsible for pulmonary infections in HIV+ patients with normal CD4+ counts?
A
- Strep. Pneumoniae
- Gm positive, Catalase neg, Alpha Hemolytic, Bile-Esmulin negative, Optochin Susceptible, Quellung positive, IgA Protease
5
Q
What are the organisms responsible for pulmonary infections in HIV+ patients with CD4+ counts less than 200?
A
- Pneumocystis jirovecii pneumonia (PCP)
- Histoplasmosis (Histoplasma capsulatum)
- Fungus found in bird/bat fecal material, and soil.
- Toxoplasmosis (Toxoplasma gondii Encephalitis)
- Parasite that usually comes from cats (they can only reproduce in cats → shed in cat’s feces )
- Invasive Aspergillosis (Aspergillus)
- common mold (a type of fungus) that lives indoors and outdoors
6
Q
What are the organisms responsible for pulmonary infections in HIV+ patients with CD4+ counts less than 50?
A
- Mycobacterium avium infection
- Interstitial Pneumonia- CMV
- Cytomegalovirus, HHV-5, dsDNA
7
Q
What are the agents that can cause TB?
A
- M. tuberculosis - cause great majority of human disease
- M. africanum - causes human tuberculosis (TB) in tropical Africa
- M. bovis - primarily isolated from cattle but causes 1%-2% of TB disease
8
Q
What are the parameters of a tuberculin test (define PPD)? How are they interpreted?
A
- PPD test for purified protein derivative
- 5+ mm is positive in:
- HIV-positive person
- Persons with recent contacts with a TB patient
- Persons with nodular or fibrotic changes on chest X-ray consistent with old healed TB
- Patients with organ transplants, and other immunosuppressed patients
- 10+ mm is positive in:
- Recent arrivals (less than five years) from high-prevalence countries
- IV drug users
- Residents and employees of high-risk congregate settings (e.g., prisons, nursing homes, hospitals, homeless shelters, etc.)
- Mycobacteriology lab personnel
- Persons with clinical conditions that place them at high risk (e.g., DM, prolonged corticosteroid therapy, leukemia, ESRD, chronic malabsorption syndromes, etc.)
- Children <4 yoa, or children & adolescents exposed to adults in high-risk categories
- 15 mm or more is positive in:
- Persons with no known risk factors for TB
9
Q
How do you calculate and interpret a positive predictive value?
A
- Calculate PPV:
- TP/(TP + FP)
- IF PPV is high → more likely that the patient actually has the condition he/she has tested positive for
- PPV increases in high prevalence settings
- IF PPV is low → more likely that your patient has tested FALSELY positive, and does not actually have the condition
10
Q
What is the MOA of Isoniazid?
A
- inhibits the synthesis of mycolic acids (essential component of bacterial cell wall)
11
Q
What is the MOA of Rifamycins?
A
- Inhibits DNA-dependent RNA polymerase.
- Four R’s:
- Ramps up P-450
- Red body fluids
- Rapid resistance
- RNA polymerase inhibitor
12
Q
What is the MOA of Pyrazinamide?
A
- Unknown.
- Thought to acidify intracellular environment via conversion to pyrazinoic acid.
13
Q
What is the MOA of Ethambutol?
A
- Decrease carbohydrate polymerization of mycobacterium cell wall by blocking arabinosyltransferase
14
Q
What is the MOA of Pyridoxine?
A
- Vitamin B6 supplement
- Given with Isoniazid to prevent neurotoxicity.
15
Q
What is the MOA of Streptomycin?
A
- Protein synthesis inhibitor:
- binds to the small 16S rRNA of the 30S subunit of the bacterial ribosome
- causes codon misreading
- Inhibits both Gram-positive and Gram-negative bacteria (bactericidal)
- First aminoglycosides discovered.
