Idiopathic Pulmonary Fibrosis (IPF) — Usual Interstitial Pneumonia (UIP pattern)

•    Clinical features:

o    Progressive exertional dyspnoea

o    Dry (non-productive) cough

o    Bilateral fine "velcro" crackles

o    Clubbing (common)

•    Imaging:

o    HRCT: subpleural, basal predominance

o    Honeycombing, traction bronchiectasis, reticular opacities

•    Prognosis: poor; median survival ~3–5 years

•    Management:

o    Antifibrotic agents: pirfenidone, nintedanib

o    Oxygen therapy, pulmonary rehab

o    Lung transplantation in selected cases

Non-Specific Interstitial Pneumonia (NSIP)

•    Histology: uniform interstitial inflammation and fibrosis (no honeycombing early)

•    More common in connective tissue diseases (e.g., scleroderma, dermatomyositis)

•    Prognosis: better than IPF/UIP

•    Management:

o    Steroids ± immunosuppressants (e.g., azathioprine)

Hypersensitivity Pneumonitis (Extrinsic Allergic Alveolitis)

•    Causes:

o    Bird fancier’s lung (avian proteins)

o    Farmer’s lung (mouldy hay)

o    Mushroom workers, hot tub lung

•    Clinical forms:

o    Acute: flu-like symptoms, cough, dyspnoea, fever within hours of exposure

o    Chronic: insidious breathlessness, weight loss, progression to fibrosis

•    Investigations:

o    HRCT: ground-glass changes, centrilobular nodules

o    Serum precipitating IgG antibodies

o    Lung biopsy: poorly formed non-caseating granulomas

•    Management:

o    Antigen avoidance

o    Steroids for severe or persistent symptoms

Sarcoidosis

•    Pathology: non-caseating granulomas affecting lungs and multiple organs

•    Respiratory:

o    Bilateral hilar lymphadenopathy (classic)

o    Pulmonary infiltrates

•    Extra-pulmonary:

o    Skin: erythema nodosum, lupus pernio

o    Eye: uveitis

o    Hypercalcaemia (macrophage-mediated vitamin D activation)

o    Neurological: cranial nerve palsies (esp. CN VII)

•    Lab:

o    ↑ ACE levels (non-specific)

o    ↑ serum calcium

o    Restrictive PFT pattern ± reduced DLCO

•    Syndromes:

o    Lofgren’s syndrome: erythema nodosum, bilateral hilar lymphadenopathy, fever, arthralgia (good prognosis)

o    Heerfordt’s syndrome: uveitis, parotid enlargement, fever, cranial nerve palsy

•    Management:

o    Observation if asymptomatic

o    Steroids if symptomatic or organ dysfunction

Histiocytosis X (Langerhans Cell Histiocytosis)

•    Population: young adult smokers (20–40 years)

•    Clinical:

o    Dry cough, dyspnoea

o    Recurrent pneumothorax (due to cyst rupture)

o    Diabetes insipidus (if pituitary stalk involvement)

•    Imaging:

o    Nodules and cysts, upper/mid-lung predominance

o    Sparing of costophrenic angles

•    Management:

o    Smoking cessation (may halt progression)

o    Lung transplant in advanced cases

Drug-Induced Pulmonary Fibrosis

•    Common culprits:

o    Amiodarone: also causes hyper/hypothyroidism

o    Methotrexate: monitor lung function

o    Nitrofurantoin: especially with chronic use

o    Bleomycin

o    Cyclophosphamide

•    Presentation:

o    Dry cough, dyspnoea

o    Restrictive pattern on PFTs

•    Management:

o    Stop offending drug

o    Consider steroids

Extra Revision Pearls

•    Honeycombing on HRCT → think UIP/IPF

•    Upper-lobe predominant fibrosis → sarcoidosis, hypersensitivity pneumonitis, Langerhans cell histiocytosis, silicosis, TB

•    Lower-lobe predominant fibrosis → IPF, asbestosis

•    ACE levels are raised in sarcoidosis but not specific; may also rise in TB and lymphoma

•    Clubbing common in IPF, rare in sarcoidosis

•    Recurrent pneumothorax in young smoker → think Langerhans cell histiocytosis

•    Lofgren’s syndrome in sarcoidosis → excellent prognosis; usually resolves spontaneously