A 28-year-old woman with SLE develops progressive shortness of breath over 6 weeks. CT pulmonary angiography is negative for PE. HRCT shows bilateral lower lobe ground-glass opacities. BAL shows haemosiderin-laden macrophages. Complement levels are low. The MOST likely diagnosis is:

• A Lupus pneumonitis
• B Shrinking lung syndrome
• C Pulmonary hypertension
• D Diffuse alveolar haemorrhage (DAH) ✓

Explanation

Diffuse alveolar haemorrhage (DAH) in SLE presents with dyspnoea, haemoptysis (may be absent), bilateral infiltrates on imaging, and haemosiderin-laden macrophages on BAL — the hallmark finding. It is associated with active lupus (low complement, high anti-dsDNA). DAH carries a high mortality and requires urgent high-dose corticosteroids ± cyclophosphamide or rituximab. Shrinking lung syndrome presents with raised hemidiaphragms and restrictive pattern without alveolar infiltrates. Lupus pneumonitis does not produce haemosiderin-laden macrophages.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.