Crazy paving

Crazy paving refers to the appearance of ground-glass opacity with superimposed interlobular septal thickening and intralobular septal thickening, seen on chest HRCT. It is a non-specific finding that can be seen in a number of conditions. 

Pathology

Etiology

Common causes:

• acute respiratory distress syndrome (ARDS)
• bacterial pneumonia
• acute interstitial pneumonia: ARDS of unknown etiology
• pulmonary alveolar proteinosis (PAP): rare, but the great majority of patients with PAP demonstrate crazy paving

Less common causes:

• drug-induced pneumonitis
• radiation pneumonitis
• pulmonary hemorrhage / diffuse pulmonary hemorrhage
  • Goodpasture syndrome
• chronic eosinophilic pneumonia
• usual interstitial pneumonia (UIP) with superimposed diffuse alveolar damage
• pulmonary edema
• pulmonary infections
  • mycoplasma pneumonia
  • obstructive pneumonia
  • tuberculosis
  • Pneumocystis jirovecii pneumonia (PCP)
  • COVID-19
• cryptogenic organizing pneumonia (COP, formerly BOOP)
• invasive mucinous adenocarcinoma of the lung (formerly mucinous bronchoalveolar carcinoma
• sarcoidosis, especially alveolar sarcoidosis
• lipoid pneumonia
• pulmonary veno-occlusive disease