A Race Against Time: Tocilizumab Rescue in Life-Threatening Antineutrophil Cytoplasmic Antibody (ANCA)-Associated Diffuse Alveolar Haemorrhage

Diffuse alveolar haemorrhage (DAH) is a potentially life-threatening manifestation of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), particularly when accompanied by glomerulonephritis.The role of interleukin-6 receptor blockade in AAV-associated DAH remains uncertain.We report a previously healthy 24-year-old woman who presented with haemoptysis, dyspnoea, severe anaemia, acute kidney injury, haematuria, and bilateral pulmonary ground-glass opacities, raising strong clinical suspicion of DAH.Renal biopsy demonstrated necrotizing glomerulonephritis with focal crescent formation, and C-ANCA was positive at a titre of 1:80.Despite intravenous methylprednisolone (500 mg daily, Days 0-2), her respiratory condition deteriorated on Day 3, with oxygen saturation declining to 88% on room air.Cyclophosphamide was proposed but declined by the patient.Intravenous tocilizumab 400 mg was subsequently administered off-label, followed by rapid respiratory improvement, with oxygen saturation increasing to 96% on room air within 24 hours.However, renal dysfunction continued to progress, necessitating additional treatment with mycophenolate mofetil, plasma exchange, and rituximab.Serum creatinine improved to 150 µmol/L by discharge on Day 25.At the latest follow-up in July 2026, the patient remained clinically well without relapse, with serum creatinine of 75 µmol/L, normal urinalysis, negative ANCA testing, and no immunosuppressive therapy since December 2025.This case highlights a striking temporal association between tocilizumab administration and rapid pulmonary improvement despite ongoing renal deterioration.IL-6 receptor blockade may have contributed to control of the acute inflammatory pulmonary process; however, causality cannot be established from a single case, and further investigation is warranted.