| Direct pulmonary involvement |
| ILD |
| ILD with PH |
| PH |
| Airways disease |
| Pleural involvement |
| Indirect pulmonary complications |
| Gastro-oesophageal reflux and aspiration |
| Infection |
| Drug toxicity |
| Malignancy |
| Respiratory muscle weakness |
| Restrictive lung disease from skin involvement |
| Secondary to cardiac involvement |
| Combination of direct and indirect pulmonary involvement |
| Other lung diseases unrelated to systemic sclerosis |
| COPD/emphysema |
| Asthma |
| Pulmonary nodules |
ILD: interstitial lung disease; PH: pulmonary hypertension; COPD: chronic obstructive pulmonary disease.