SPECIAL SELECTED TOPICS- RESPIRATORY SYSTEM DISORDERS-SSTRSDO-QAA 020
1.
Describe the difference between usual interstitial pneumonia (UIP) and
desquamative interstitial pneumonia (DIP).
interstitial pneumonia
desquamative interstitial pneumonia
Usual interstitial pneumonia (UIP) is the histologic pattern
of idiopathic pulmonary fibrosis and is characterized by patchy interstitial
fibrosis with marked temporal heterogeneity.
Normal lung alternates with areas of active fibroblast
proliferation and dense fibrosis. Honeycomb lung is a prominent feature of
advanced UIP. The prognosis is poor because fibrosis progresses relentlessly.
Desquamative interstitial pneumonia (DIP) is strongly
associated with cigarette smoking. It is characterized by diffuse accumulation
of macrophages within alveolar spaces rather than true desquamation of
epithelial cells. Interstitial fibrosis is mild and relatively uniform.
DIP responds well to smoking cessation and corticosteroid
therapy. The prognosis of DIP is considerably better than that of UIP.
2. Define
hypersensitivity pneumonitis.
Hypersensitivity pneumonitis, also called extrinsic allergic
alveolitis, is an immunologically mediated inflammatory disease caused by
repeated inhalation of organic antigens.
Common antigens include moldy hay, bird proteins, fungi, and
contaminated humidifiers. Both type III immune complex and type IV delayed
hypersensitivity reactions contribute to the disease. Inflammation primarily
affects the alveoli and interstitium. Patients present with fever, cough,
dyspnea, and malaise several hours after antigen exposure.
Chronic exposure leads to interstitial fibrosis and
restrictive lung disease. Histology shows interstitial inflammation with poorly
formed non-caseating granulomas. Avoidance of the offending antigen is the
cornerstone of treatment. Corticosteroids are useful in severe or persistent
cases.
PROFESSOR OF MEDICINE
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