Interstitial lung disease Flashcards
Interstitial Lung Diseases (ILD)
general
Collection of disorders that involves inflammation and scarring (fibrosis) of the lung interstitium (the space between the capillaryendotheliumand the alveolarepithelium
The lung becomes “stiff” (reduced distensibility) and compromises lung expansion
Causes
Idiopathic or secondary to connective tissue diseases, medications, malignancies, occupational exposure, or allergens
ILD
pattern on spirometry
Restrictive pattern on spirometry
Normal FEV1/FVC ratio (> 0.70) and a reduction in TLC below 80% of the predicted value
Decreased diffusion capacity for carbon monoxide (DLCO)
Impaired gasdiffusionacross the alveolar membrane:
Idiopathic pulmonaryfibrosis (IPF)
general and RF
Characterized by chronic, progressive, irreversiblefibrosis (“scar tissue”) of the lung parenchyma
Epidemiology:
Estimatedprevalencein the United States: 10–60 per 100,000
Occurs primarily in elderly individuals
Commonly diagnosed in the 50-60 years old
Men > Women
Risk factors: male, advanced age, history of tobacco use
Idiopathic pulmonaryfibrosis
patho
The mechanism triggering IPF is poorly understood
Environmental exposure and possible genetic predisposition
Recurrent alveolar epithelial damage → type I pneumocytes release transforming growth factor beta1 → proliferation of type II pneumocytes → stimulate fibroblasts that are found in the interstitial tissue
Activated fibroblastsdevelop into myofibroblast (fibroblasts with smooth muscle cell properties)
Myofibroblast secrete:
Reticular fibers - a type of collagen which provides structural strength
Elastic fibers - provide the rubber-band like elasticity of the lungs
Failure of normal myofibroblastapoptosis→ accumulation of collagen leads to thickening of the interstitial layer
Consequences:
Restrictive lung - poor air in and out of the lung
↓gas exchange
Fundamental problem….too many myofibroblasts and too much collagen!
Idiopathic pulmonaryfibrosis
clin man
progressive disease
Asymptomatic early in the disease process
Moderate to advanced stage:
Chronic dyspnea-Initially exertional, Progressive, eventually occurring at rest
Chronic nonproductive cough
Reduced exercisetolerance
Chest pain
Associated systemic symptoms (uncommon):
Fatigue
Low-grade fever
Weight loss
Myalgias
will lead to r sided heart failure and pulm HTN
Idiopathic pulmonaryfibrosis
PE findings
Auscultation
secondary disease sx
Bibasilar fine inspiratory (“Velcro-like”) crackles on auscultation
End-inspiratory “squeaks” in advanced disease withbronchiectasis
Digitalclubbing
Cyanosis
Patients can present withpulmonary hypertension (PH) andcor pulmonale:
Pitting edema (pedal or sacral)
Jugular venous distention
Cyanosis
Split second heart sound
(this is later as disease progresses)
Idiopathic pulmonaryfibrosis
Hx Dx
Med use
Diagnosed by a combination of radiologic, pathologic, and clinical investigations
Critical to obtain a complete patient history
Occupational history
Recreational history
Environmental history
Radiationexposure
Notable medications associated with pulmonary fibrosis:
Amiodarone
Bleomycin
Nitrofurantoin
Methotrexate
Idiopathic pulmonaryfibrosis –
Diagnosis Spirometry
Pulmonary function test
Reveals ↓ lung volumes (restrictive pattern):
Vital capacity
Total lung capacity(TLC)
Forcedvital capacity(FVC)
Forced expiratory volume in 1 sec
FEV1/FVC ratio is greater than 80% (increased) due to a significant decrease in forced vital capacity (FVC)
Idiopathic pulmonaryfibrosis
imaging
Chestx-ray
May look normal in early disease
Reticulonodular infiltrates
Bilateral, basal, and symmetrical
High-resolution CT scan
Significantly more sensitive and specific
Features (predominantly seen in the lower lobes):
Peripheral and subpleural reticular septal thickening
Tractionbronchiectasis
Honeycombing
Lung architecturaldistortion
Superimposed ground-glass opacities may be seen
Idiopathic pulmonaryfibrosis
biopsy and labs
Lung biopsy- best for Dx
Surgical specimens can be obtained using video-assisted thoracoscopic surgery (VATS)
Supporting laboratory evaluation to exclude other causes ofILD and guide management:
Erythrocyte sedimentation rateand CRP
Antinuclearantibodies
Rheumatoid factorand anti–cyclic citrullinated peptideantibodies
Aldolaseand CK
Myositis-specificantibodies
Anti-SSA/Ro and anti-SSB/Laantibodies
Serum ACE level
pulmonologist would do this
Idiopathic pulmonaryfibrosis
lifestyle mods
Smoking cessation
Vaccinations: influenza, Covid-19, and pneumonia
Idiopathic pulmonaryfibrosis
Tx
Antifibrotic drugs
Approved for delaying progression
Do not significantly improvemortality
Oxygen therapy
Indicated when the patient’sresting or ambulatory oxygen saturation are < 88%
Lung transplant
Only definitive treatment
Bilaterallung transplantationis more commonly used than singlelung transplantation
Early referral should be considered
Sarcoidosis
general
Multisystem inflammatory disease characterized by the formation ofnoncaseating granulomas that are most likely caused by a cell-mediated immune reaction
Etiology is undetermined but is most likely multifactorial
more common in african american women
Potential triggering exposure: environmental exposure or infectious agent
Genetic predisposition
sarcoidosis
pulmonary or extrapulmonary
Pulmonary sarcoidosisis a restrictive interstitial lung disease with granuloma formation in the:
Lungs(90% ofpatients)
Thoraciclymph nodes(hilar and mediastinal)
Extrapulmonary sarcoidosisis characterized by granuloma formation in:
Eyes – uveitis
Skin – erythema nodosum; macular or papular lesions
Joints
Heart – arrhythmias
Kidney
CNS andperipheral nervous system
Exocrine glands
sarcoidosis
Patho
Phagocytosisof a newantigenbyantigen-presenting cells (macrophagesanddendritic cells)
Activated macrophages present the antigento helper T cellsvia the HLA-CD4 complex
Activated T cellsandmacrophagesrelease inflammatory mediators (Th1response):
Interleukin 2 (IL-2)
Interferon gamma
Tumornecrosisfactor (TNF)
Othercytokinesandchemokines
Inflammatory mediators causemacrophagesto fuse into multinucleatedgiant cells
Unable to destroy the antigens, the multinucleatedgiant cellswall them off →noncaseating granulomaformation
Fibroblasts are recruited and surround granulomas and may progress tofibrosis
NON CASEATING