Piper's Lung: Marijuana-Associated Interstitial Pulmonary Fibrosis

Piper's lung is a rare form of interstitial pulmonary fibrosis linked to chronic marijuana smoking.

Histopathology

• Birefringent lipid-laden macrophages and extracellular lipid deposits along alveolar septa and in small airway lumina.
• Associated with thermal degradation products of cannabis resins and oils—not cannabinoids themselves.
• Pattern: mixed cellular/fibrosing interstitial pneumonia; may mimic hypersensitivity pneumonitis or nonspecific interstitial pneumonia (NSIP).

Clinical Presentation

• Insidious dyspnea, cough, restrictive physiology on pulmonary function tests.
• HRCT: ground-glass opacities, reticulation, traction bronchiectasis (basilar predominance).
• Diagnosis requires exposure history, compatible histology, and exclusion of other interstitial lung diseases.

Management

• Cessation of marijuana smoking (vaporization may reduce but not eliminate risk).
• Corticosteroids or immunosuppressants if progressive (limited evidence).
• Monitor for progression to honeycombing and respiratory failure.

Underreporting due to stigma and illegality is common; clinicians should inquire about inhalation habits in unexplained interstitial lung disease.