Hypersensitivity Pneumonitis
- causes and risk factors
- signs and symptoms/diagnosis
- pathophysiology
- treatments
- course
- patient education
- community resources
- references
Hypersensitivity pneumonitis, also known as extrinsic allergy alveolitis, is an immunologically-indiced lung disease by fine organic dust particles.
Causes and Risk Factors
Numerous causative substances have been identified:
- farmer's lung: moldy hay (Thermophilic actinomyces) : 0.1-1/1000 farmers exposed
- bagassosis
- wood worker's
- compost lung: Aspergillis
- tea grower's lung
- office worker's lung: ventilation/humidifiers/air conditioners, and associated sp
- grain worker's lung
- bird fancier's lung
- lab worker's lung: rat fur or urine proteins
- TDI lung
- drug related: antibiotics
~10% regularly exposed hosts develop EAA
Signs and Symptoms/Diagnosis
Acute form: 4-6 hours after intense exposure: fever, chills, malaise, dyspnea, dry cough, lasting 24 hours. Chest X ray is normal or with bilateral mixed interstitial and airspace opacities. ABG show hypoxemia. It is often misdiagnosed as infectious pneumonia.
Subacute: insidious onset cough, sputum, exertional dyspnea, weight loss, fine crackles, PFT restriction and decreased DLCO
Chronic: irreversible disease, progressing to cor pulmonale and respiratory failure. Interstitial fibrosis leads to peripheral opacities on chest X ray. PFT shows mixed reactive and obstructive patterns.
Pathophysiology
granulmoas suggests type IV hypersensitivity.
abnormalities suggests lymphocytic alveolitis: low CD4+/CD8+
Treatments
Recognize and avoid antigen exposure.
Wear a SCBA if avoidance is impossible.
Low dose systemic steroids can be used to control symtoms
Course
Chronic hypersensitivity pneumonitis is a serious condition.
Patient Education
Community Resources
References