Hypersensitivity Pneumonitis -Goya Flashcards
What is hypersensitivity pneumonitis?
inhaled dust or chemicals that produces an immunologically mediated inflammatory response of the alveoli and terminal bronchioles
What is acute hypersensitivity pneumonitis? What is an example?
- Most classic & easily recognized form of HP
- Symptoms characteristically occurs 4-6 hours after initial heavy exposure
- removal of exposure results in subsiding symptoms within 12 hours to several days
- Example: farmer’s lung
A 22-year old college student went for cave exploration during vacation. On the first day evening he went to nearby urgent care with acute SOB and mild fever. His vitals were stable and his chest x-ray shows diffuse bilateral infiltrate. He was given some bronchodilator and symptoms resolved by next day morning. Which of the following was most likely diagnosis? A. Idiopathic pulmonary fibrosis B. Sarcoidosis C. Hypersensitivity pneumonitis D. Tuberculosis
C. Hypersensitivity pneumonitis
what is the clinical presentation of subacute HP?
Characterized by gradual development of productive cough, dyspnea, fatigue, anorexia & weight loss
CXR maybe similar to acute HP
Similar findings may occur in patients who suffer repeated, infrequent acute attacks of HP
what is the clinical presentation of chronic HP?
May lack a history of acute episodes
Continuous or low intensity exposure for months to years (hot tub lung)
Insidious onset of cough, dyspnea, fatigue & weight loss
Fever or chills are usually absent
May progress to severe pulmonary fibrosis or cor pulmonale & may be difficult to differentiate from IPF
What are the PE findings in HP?
rales at the onset or shortly after acute exposure
rales persist for weeks after an acute attach or during the chronic stages
will not find rales when the pt is asymptomatic or when the CXR is normal
What are the lab findings in HP?
no single lab test
WBC range from 12,000-15,000 (eosinophilia is rare)
ESR will be elevated in acute HP but normal in subacute or chronic
What are the typical CXR findings in HP? Does a normal chest x-ray exclude an HP diagnosis?
no!
CXR has a low sensitivity in acute and subacute HP
symptoms are likely to be worse than the CXR
CXR in acute or subacute HP may show fine reticular pattern with multiple small defined nodules
Nodular shadows are usually diffuse, involving the middle & lower lung zones
With progression, the infiltrate will take a more coarse interstitial pattern or “honey-combing”
What will acute, subacute and chronic HP look like on high resolution CT?
Acute HP & subacute HP may show bilateral air-space consolidation, ground glass opacity & small ill-defined centrilobular nodules
Chronic HP often mirror those of IPF with honeycombing, irregular reticular opacities, traction bronchiectasis, ground glass opacity
What will the PFT findings be in HP?
acute attack=restrictive pattern
hypoxemia may be present
resp alkalosis is common
PFT abnormalities 4-6 hours after exposure and will show improvement 12-18 hours after removal of exposure
complete resolution in 1-6 months
What is a common histopathology finding in HP?
noncaseating granulomas
advanced stages have interstitial fibrosis
What is the diagnostic criteria for HP?
Characteristic signs & symptoms, radiographic findings and PFT data
Evidence of exposure to relevant antigen with plausible temporal relationship to clinical findings
Exclusion of other related illness
What is the treatment for HP?
antigen avoidance and corticosteroids
What are some helpful clues in recognizing HP?
History of recurrent atypical pneumonia, particularly if there is regularity to the illness (eg only in spring or fall, only certain time of week or following certain events)
Symptoms developed after moving to new job or home
Pets, especially birds, even if patient denies contact with pet (can include feather pillows, down blankets)
History of water damage to home or office, particularly to crawl space, basement, roof, ceiling tiles, carpet
Use of hot tub, sauna, swimming pool
Other people having similar symptoms or have left work because of recurrent symptoms
Patient feels better when away from home or work (vacation)
How does cigarette smoking affect the risk of HP?
higher frequency of HP in non-smokers than smokers
diminished antibody response to inhaled antigens due to the cigarette smoke
