Pulmonary vasculitis and diffuse alveolar haemorrhage

• Diffuse alveolar haemorrhage (DAH) is bleeding into the alveolar spaces; it presents with haemoptysis, falling haemoglobin, new diffuse infiltrates and hypoxaemia, and is life-threatening.
• The classic pulmonary-renal syndrome group is granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and anti-glomerular basement membrane (anti-GBM) disease; systemic lupus erythematosus (SLE) and the antiphospholipid syndrome are the other common autoimmune causes. ^[1]
• DAH is not one disease: it is either a pulmonary capillaritis (vasculitic, ANCA- or immune-complex mediated) or bland haemorrhage (no vessel inflammation), and the distinction drives treatment.
• Bronchoscopy with bronchoalveolar lavage, showing bleeding in sequential aliquots, is the diagnostic gold standard; high-resolution CT and an active urinary sediment complete the work-up.
• Treatment is urgent immunosuppression: high-dose intravenous methylprednisolone 500–1000 mg/day for 3–5 days plus cyclophosphamide or rituximab for GPA/MPA; plasma exchange (PLEX) plus cyclophosphamide and oral prednisolone for anti-GBM disease; and pulse glucocorticoids plus cyclophosphamide or rituximab for SLE-associated DAH. ^[1][3][4]

By the end of this page you should be able to:

1. Define diffuse alveolar haemorrhage, separate it from haemoptysis of airway origin, and sort it into capillaritis-mediated and bland haemorrhage.
2. Explain the pulmonary and renal pathology of GPA, MPA, anti-GBM disease and SLE, and why they are grouped as pulmonary-renal syndromes.
3. Build a focused differential diagnosis for a patient with DAH and identify the clinical clues that point to each cause.
4. Plan investigations, including bronchoscopy with bronchoalveolar lavage, imaging, serology and renal biopsy, and interpret the results.
5. Choose immediate, induction and maintenance treatment for GPA, anti-GBM disease and SLE-associated DAH, with doses, routes and durations.
6. Recognise the controversies, including the place of plasma exchange, and outline low-resource alternatives.
7. Identify complications, prognosis and follow-up for each condition.

Vasculitis is inflammation of the wall of a blood vessel. In the lung, small-vessel vasculitis damages the alveolar capillaries: red cells leak into alveoli, producing the clinical syndrome of diffuse alveolar haemorrhage. DAH is uncommon but catastrophic, with high short-term mortality, and it is the presentation that most often forces the diagnosis of a systemic vasculitis or autoimmune disease to be made in an intensive care unit. ^[1][2]

This page concentrates on the three causes that together dominate pulmonary vasculitis and DAH: granulomatosis with polyangiitis (GPA), anti-GBM disease (the condition historically called Goodpasture syndrome when it affects the lung) and systemic lupus erythematosus (SLE). The surrounding diseases—microscopic polyangiitis, eosinophilic granulomatosis with polyangiitis, the antiphospholipid syndrome—are mentioned where they change the differential or the management. General vasculitis nomenclature and the other organ-limited vasculitides are covered in the musculoskeletal chapter's vasculitis topic; renal aspects, including rapidly progressive glomerulonephritis, are covered in the renal chapter topic on nephritic syndrome.

Diffuse alveolar haemorrhage is the clinical-pathological state in which bleeding occurs from the alveolar capillaries into the airspaces, producing diffuse pulmonary infiltrates, a falling haemoglobin and (often, but not always) haemoptysis. ^[1] It is a syndrome, not a diagnosis: the underlying cause must be sought.

Pulmonary vasculitis proper is inflammation of the pulmonary vessels. In alveolar haemorrhage two histological patterns dominate:

• Pulmonary capillaritis, a necrotising inflammation of the alveolar septal capillaries, usually immune-mediated, which fragments the capillary wall and spills red cells into alveoli.
• Bland haemorrhage, with no vessel inflammation; red cells enter because of mechanical or coagulation failure rather than vessel wall destruction.

Up to 73% of lupus-associated DAH cases show the bland pattern without overt vasculitis. ^[1]

The Chapel Hill 2012 nomenclature places these diseases in the immune-mediated groupings a student should recognise:

• ANCA-associated small-vessel vasculitis: GPA, MPA and EGPA. These are pauci-immune (few or no immune deposits) and associated with PR3- or MPO-ANCA.
• Immune-complex small-vessel vasculitis: anti-GBM disease, cryoglobulinaemic vasculitis, IgA vasculitis and hypocomplementaemic urticarial vasculitis. Anti-GBM disease is a vasculitis affecting glomerular capillaries, pulmonary capillaries, or both. ^[6]

GPA is characterised histologically by necrotising granulomatous inflammation in addition to vasculitis and clinically by destructive sino-nasal lesions, pulmonary nodules and pauci-immune glomerulonephritis. MPA has vasculitis without granulomatous inflammation, with rapidly progressive pauci-immune glomerulonephritis and alveolar haemorrhage as typical manifestations. ^[4]

The precise incidence of DAH is unknown because it is defined as a syndrome and usually occurs in the setting of an underlying disease. AAV and SLE are rare. In European populations the recorded prevalence of GPA is 24 to 157 per million, with the highest prevalence reported in Sweden and the United Kingdom. ^[4] MPA ranges from 0 to 66 cases per million among European countries and 86 cases per million in Japan. ^[4]

The one epidemiologic fact that matters at the bedside is that DAH is the single most dangerous pulmonary complication of each of these diseases: a multicentre retrospective cohort of 197 patients with severe AAV-related DAH (respiratory symptoms, new infiltrates consistent with alveolar haemorrhage and oxygen saturation at most 85%, high-flow oxygen or mechanical ventilation) reported median age 66 years and 52% women, and mortality differed significantly between three clinical phenotypes. ^[2]

A workable bedside list, grouped by mechanism, is the following. ^[1]

Immune-mediated capillaritis (pulmonary-renal and connective-tissue disease).

• Granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA).
• Anti-GBM disease (Goodpasture syndrome is the term when both lung and kidney are involved).
• Systemic lupus erythematosus and the antiphospholipid syndrome.
• IgA vasculitis (unusual, but pulmonary haemorrhage can be part of it).

Pulmonary capillary stress or mechanical failure.

• Mitral stenosis and elevated left-atrial pressure (rare, dramatic haemorrhage).
• Malpositioned pulmonary artery catheter.

Bland or clotting-related haemorrhage.

• Coagulopathy (anticoagulants, thrombocytopenia, disseminated intravascular coagulation).
• Drugs and toxins (amiodarone, cyclophosphamide in a documented pulmonary toxicity pattern, crack cocaine, some biologics).

Infection, particularly in immunosuppressed patients.

• Bacterial pneumonia, invasive aspergillosis, viral infection and (in children) idiopathic pulmonary haemosiderosis. These must be excluded rather than treated as a vasculitis.

Non-immune acute lung injury.

• Acute respiratory distress syndrome mimics with alveolar haemorrhage can be indistinguishable at the bedside from ARDS; bronchoscopy and cardiac imaging separate them.

Risk factors for GPA are not modifiable in the ordinary sense, but environmental triggers such as silica exposure, infection and certain drugs have been linked to AAV onset. ^[2] Female sex and young-to-middle age are typical for SLE. ^[5]

In GPA the initiating injury is a necrotising granulomatous inflammation of small- to medium-sized arteries, capillaries and venules, driven in most cases by antibodies to proteinase 3 (PR3-ANCA). Neutrophil activation damages the endothelial lining of the alveolar capillaries, the wall fragments, and red cells escape into alveolar spaces. The same inflammation organises into granulomas and, in the upper airway, into destructive lesions. Granulomas can involve larger pulmonary vessels and, when they necrose, leave cavitated nodules that are the radiological signature of GPA. ^[4]

Anti-GBM disease is a prototype of the type II hypersensitivity (antibody-mediated) mechanism. Autoantibodies are directed against the non-collagenous domain of the α3 chain of type IV collagen in basement membranes. The antigen is shared between glomerular and alveolar basement membranes, which is why the disease attacks both organs. The antibody fixes complement and produces a linear immunoglobulin deposition on the basement membrane; capillary destruction and haemorrhage follow. Pulmonary involvement occurs in 40 to 60% of patients. ^[3]

In SLE the lung injury is more often bland than vasculitic. Immune-complex deposition with complement activation produces microvascular damage, but most pulmonary bleeding is "true" haemorrhage without well-formed vasculitis, especially in the absence of ANCA. ^[1] Complement consumption (low C3, low C4) and active systemic disease (nephritis, serositis) frame the clinical picture.

The classic triad of DAH is haemoptysis, anaemia and new diffuse infiltrates, although haemoptysis may be absent at the bedside. ^[1]

• Haemoptysis can be massive (blood clots, Asphyxiation risk) and often comes in paroxysms; in DAH the blood is less viscid and fresher than airway bleeding.
• Breathlessness and cough, often of acute or subacute onset; fever is common and can be confused with infection.
• Anaemia out of proportion to visible blood loss is a strong clue: a falling haemoglobin in a patient with new bilateral infiltrates is DAH until proven otherwise.

Organ clues sort the cause:

• GPA: chronic or acute sinus disease, nasal crusting and epistaxis, deafness, tracheobronchial symptoms, stridor; joints, skin and eyes can be involved.
• Anti-GBM disease: simultaneous haematuria, red-cell casts, rising creatinine (a true pulmonary-renal syndrome); often in young smokers, among whom pulmonary capillary permeability is higher.
• SLE: the 2019 EULAR/ACR classification criteria context (fever, serositis, arthritis, cutaneous and renal disease, cytopenias) and a flare of known lupus.

• Reduced oxygen saturation, diffuse crackles, tachypnoea.
• Signs of systemic vasculitis: purpura, mononeuritis, sinus tenderness, nephritic oedema.
• A cardiac murmur may point to mitral stenosis as a bland cause.

GPA can affect the conducting airways directly: tracheobronchial stenosis presents with stridor, wheeze and fixed airflow limitation, and is reported in case series of tracheobronchial disease. ^[4] Imaging of GPA shows pulmonary nodules that are often multiple and cavitated, reflecting necrotising granulomas.

The bedside question is whether the patient has DAH or something that looks like DAH (ARDS, cardiogenic oedema, severe pneumonia), and, if it is DAH, which cause.

• Full blood count and coagulation profile: a falling haemoglobin confirms bleeding; check platelets and clotting.
• Urea and electrolytes, creatinine, estimated GFR and urinalysis: look for red-cell casts and proteinuria, which place the patient in the pulmonary-renal group. In anti-GBM and ANCA disease the complement levels are usually normal; in SLE, C3 and C4 are often low.
• Arterial blood gas: quantify hypoxaemia.
• Chest radiograph: diffuse or patchy alveolar opacities, often bilateral; normal in a minority.

A high-resolution CT (HRCT) of the chest is more useful than the chest film. Look for ground-glass opacities and consolidation, sometimes with the "crazy-paving" pattern (ground glass with superimposed interlobular septal thickening), which appears as haemorrhage resolves. ^[1] Nodules and cavities point to GPA; in anti-GBM disease the infiltrates are diffuse and homogeneous.

Bronchoscopy with BAL remains the diagnostic gold standard, confirming haemorrhage in sequential aliquots. ^[1] The lavage returns progressively bloodier or more haemosiderin-laden fluid across the aliquots, with red blood cells and haemosiderin-laden macrophages. The BAL also excludes infection, which may be the whole illness.

Do not wait for bronchoscopy to start treatment in a crashing patient.

• ANCA by indirect immunofluorescence and by ELISA for PR3 and MPO. A positive ANCA in the right clinical context supports GPA or MPA; it is not sufficient on its own.
• Anti-GBM antibodies in serum. A positive result is strong evidence; biopsy may still be needed in seronegative cases.
• ANA, anti-dsDNA, complement C3/C4, antiphospholipid antibodies for SLE and the antiphospholipid syndrome.
• Anti-GBM and ANCA can co-occur (double-positive disease), which carries a prognosis closer to anti-GBM disease.

Where the kidney is involved, biopsy is diagnostic and prognostic. The characteristic pictures are: linear IgG along the GBM in anti-GBM disease; pauci-immune necrotising crescents in ANCA disease; and "full house" immune deposits in SLE. See the renal chapter topic on nephritic syndrome for interpretation and the KDIGO approach to rapidly progressive glomerulonephritis.

• Pulmonary function tests, in stable patients, show restriction; the DLCO may be raised acutely (because bleeding increases the capillary membrane transit) and a reduced DLCO in recurrent disease suggests fibrosis. ^[1]
• Echocardiography to exclude mitral stenosis and elevated left-atrial pressure where bland haemorrhage is suspected.
• Lung biopsy (surgical or transbronchial) is occasionally needed when the diagnosis is uncertain and therapy is toxic; histopathology shows either capillaritis or bland haemorrhage. ^[1]

There is no single "diagnostic criterion" for DAH; diagnosis rests on compatible symptoms, radiology and BAL. For GPA, MPA and EGPA, the 2022 ACR/EULAR classification criteria are widely used for classification in research; they are classification, not diagnostic, tools. For the clinician at the bedside, the working line is: compatible clinical picture plus positive ANCA or tissue biopsy. ^[4]

Severity matters because it dictates drugs:

• Severe disease in AAV includes alveolar haemorrhage, glomerulonephritis, central nervous system vasculitis, mononeuritis multiplex, cardiac involvement, mesenteric ischaemia and limb or digit ischaemia. ^[4]
• Non-severe disease includes rhinosinusitis, asthma, mild systemic symptoms, uncomplicated cutaneous disease and mild inflammatory arthritis. ^[4]

In anti-GBM disease, renal status at presentation (dialysis-dependent versus not) is the strongest predictor of renal recovery. Dialysis-dependent patients have a lower likelihood of renal recovery, and treatment decisions must weigh biopsy findings, clinical severity and contraindications to standard immunosuppression. ^[3]

• Respiratory support from oxygen through non-invasive ventilation to mechanical ventilation; many patients need prone positioning and neuromuscular blockade. In the PLEXHIA cohort of severe AAV-DAH, invasive mechanical ventilation was used in 51.8% of patients and corticosteroid pulse in 95.4%. ^[2]
• Transfusion according to standard critical care practice, bearing in mind that in the anti-GBM plasma-exchange setting McAdoo and Pusey recommend aiming for haemoglobin above 90 g/L. ^[3]
• Correct coagulopathy, stop anticoagulant and antiplatelet drugs where safe, and exclude infection before attributing a picture to vasculitis.
• Early ICU and multidisciplinary consultation (respiratory, nephrology, rheumatology, immunology) in every severe case.

The 2021 ACR/Vasculitis Foundation guideline (the edition current at the time of writing and the source for the doses below) frames severe GPA/MPA treatment as glucocorticoids plus either cyclophosphamide or rituximab. ^[4]

• Pulse glucocorticoid: methylprednisolone 500–1000 mg intravenously for 3–5 days, followed by high-dose oral prednisone 1 mg/kg/day, generally up to 80 mg/day, and tapered. ^{[4] [5]}
• Cyclophosphamide: daily oral up to 2 mg/kg/day for 3–6 months, or intermittent intravenous 15 mg/kg every 2 weeks for three doses followed by 15 mg/kg every 3 weeks for at least three doses in adults. ^[4]
• Rituximab: 375 mg/m² intravenously weekly for four doses or 1000 mg intravenously on days 1 and 15 in adults. ^[4]
• Methotrexate, azathioprine or mycophenolate are used in non-severe disease as induction instead of cyclophosphamide or rituximab. ^[4]

Rituximab is conditionally preferred over cyclophosphamide for remission induction in GPA/MPA, and routine plasma exchange is conditionally recommended against for active glomerulonephritis and for active severe GPA/MPA with alveolar haemorrhage. ^[4] This matters because earlier practice assumed PLEX was routine in DAH; the randomised evidence (PLEXIVAS) has overturned that assumption for most patients, though selected high-risk subgroups may still gain benefit and PLEX remains debated. ^[1][2]

• Gendreau and colleagues' phenotypic analysis of the PLEXHIA cohort (197 severe AAV-DAH patients) found three clusters, with the 30- and 90-day survival rates differing significantly between them and the MPO pulmonary-renal cluster carrying the highest risk of death; it also found that ANCA specificity alone is not enough to capture heterogeneity in critically ill patients. ^[2]

• Azathioprine up to 2 mg/kg/day, or methotrexate up to 25 mg/week subcutaneous or oral, or rituximab 500 mg intravenously every 6 months or 1 g every 4 months. ^[4]
• Prednisone is tapered to the lowest dose that controls disease; the duration of glucocorticoid therapy is guided by the patient’s clinical condition, preferences and values. ^[4]
• Methotrexate may be used where renal function is adequate; azathioprine is the safer choice in significant renal impairment.

The treatment standard (McAdoo and Pusey, 2025) combines plasma exchange, cyclophosphamide and glucocorticoids, with rituximab as an alternative where cyclophosphamide is contraindicated. ^[3]

• Plasma exchange every day, with an exchange volume of 60 mL/kg (replacement with albumin), adding 300–600 mL fresh frozen plasma within three days of any invasive procedure or in the presence of alveolar haemorrhage. Continue until anti-GBM antibody is fully suppressed, typically 14 days, monitoring levels during and after. ^[3]
• Cyclophosphamide 2–3 mg/kg/day (ideal body weight, maximum 200 mg) orally for 2–3 months; reduce the dose in patients over 55 years or those with dialysis-dependent kidney disease, and give the dose after dialysis or plasma exchange. Pulsed intravenous cyclophosphamide has limited evidence in this disease. ^[3]
• Prednisolone 1 mg/kg/day (maximum 60 mg) orally, reduced weekly to 20 mg by six weeks, then tapered to complete discontinuation at six months. Pulsed intravenous methylprednisolone has limited supporting evidence, provided the other components are started promptly. ^[3]
• Rituximab (2 × 1 g on days 0 and 14, or 375 mg/m² weekly for four doses) is an option where there are contraindications to cyclophosphamide or in refractory disease; PLEX should be delayed 24–48 hours after a rituximab infusion. ^[3]

The reason PLEX is central here but not in GPA is biological: the pathogenic antibody in anti-GBM disease is present in high titre in the circulation and fixes rapidly to basement membrane. Removal by apheresis, combined with suppression of new antibody formation by cyclophosphamide, addresses both ends of the process. ^[3]

Treat as a life-threatening flare of SLE. The EULAR 2023 management recommendations (summarised by Moysidou and Fanouriakis, 2024) support pulse glucocorticoids for moderate to severe disease. ^[5]

• Pulse glucocorticoid 250–1000 mg/day intravenously for 1–3 days; simpler regimens (500–1000 mg/day for 3 days) are widely used and cited in DAH reviews. ^[1][5]
• Hydroxychloroquine 5 mg/kg real body weight per day for all patients with SLE, continued long-term. ^[5]
• Oral prednisone 0.3–0.5 mg/kg/day after the pulse, tapering (the traditional 1 mg/kg regimen has not shown additional benefit because the genomic pathway is largely saturated at the lower dose). ^[5]
• IV cyclophosphamide or rituximab for life-threatening flares, and for organ-threatening disease. ^[5] (For cyclophosphamide dosing in SLE practice, the Euro-Lupus low-dose regimen is preferred where possible; follow the musculoskeletal and renal chapters for lupus nephritis details.)
• Low-dose pulse regimens (1500 mg over three days) are as effective as high-dose pulses (3000–5000 mg) and may reduce infectious complications. ^[5]

The bland pattern that dominates SLE DAH responds to immunosuppression just as well; plasma exchange is not routine and is reserved for refractory cases. ^[1]

• High-flow oxygen, non-invasive and invasive ventilation as required.
• ECMO or extracorporeal life support in refractory, reversible respiratory failure, in centres with expertise.
• Infection control and empirical antibiotics only when there is genuine clinical suspicion, because both AAV and SLE DAH can present with fever.

All three diseases need long-term, organs-specific follow-up: ANCA titres fluctuate but a rising PR3-ANCA and clinical context can herald relapse; anti-GBM antibody levels are monitored to catch rebound after PLEX; and lupus is monitored by activity scores, C3/C4 and anti-dsDNA.

• Massive pulmonary haemorrhage and respiratory failure, the immediate threat in every cause of DAH.
• Multi-organ vasculitis: in GPA, destructive sinonasal disease, orbital and central nervous system disease, mononeuritis multiplex, skin and joint involvement; in MPA, rapidly progressive kidney disease. ^[4]
• Anti-GBM disease: renal failure requiring dialysis or transplantation; recurrence in a renal allograft is unusual but pulmonary haemorrhage can recur if antibody returns.
• SLE flare morbidity: nephritis, neuropsychiatric SLE, cytopenias and infection (largely steroid- and cyclophosphamide-related).
• Treatment toxicity: bone-marrow suppression, urothelial toxicity and infertility with cyclophosphamide; infusion reactions and hypogammaglobulinaemia with rituximab; infection with high-dose glucocorticoids. ^[3][4]
• Tracheobronchial stenosis in GPA, presenting as stridor and fixed airflow limitation. ^[4]

• Anti-GBM disease has shifted from rapidly fatal to treatable: the combination of plasma exchange, cyclophosphamide and glucocorticoids has significantly improved outcomes, particularly in patients who are not dialysis-dependent at presentation. ^[3]
• AAV with severe DAH remains high-risk. In the PLEXHIA cohort, one-year outcomes were under the influence of clinical phenotype, age and organ involvement, and the phenotypes with the oldest, most hypoxaemic, renal-involved patients carried the highest short-term mortality. ^[2]
• SLE-associated DAH is life-threatening but reversible; prognosis has improved with prompt immunosuppression.
• For all three, the earlier the diagnosis (before irreversible oxygen or renal dependence) the better the outcome, which is why a "new diffuse infiltrate with falling haemoglobin" must be treated as DAH until proven otherwise.

• No vaccine or lifestyle modification prevents GPA, MPA, anti-GBM disease or SLE. Smoking cessation is sensible in general and is particularly prudent in anti-GBM disease, where many patients are young smokers and pulmonary capillary permeability may be higher.
• Screen for a second autoimmune disease at presentation: double-positive (ANCA plus anti-GBM) and ANA-positive subsets change management.
• Prophylaxis against Pneumocystis jirovecii pneumonia, and bone and gastrointestinal protection, are standard for high-dose glucocorticoid and cyclophosphamide regimens but doses and durations should follow local guidelines rather than be copied from any single source.

• Pregnancy: GPA/MPA activity in pregnancy parallels disease activity outside it. Cyclophosphamide is contraindicated in pregnancy; rituximab is used with specialist input. Anti-GBM disease is rare in pregnancy. Lupus nephritis and DAH in pregnancy are managed by a multidisciplinary team. (The nephrology and rheumatology chapters discuss pregnancy in lupus in detail; this page defers to them.)
• Children: rare; GPA and anti-GBM disease in children often present with fulminant pulmonary-renal syndrome and respond to the same induction principles in age-adjusted doses.
• Older adults: reduce cyclophosphamide dose in patients over 55 years in anti-GBM disease; infection risk is higher and steroid-sparing maintenance is correspondingly more important. ^[3]

• A chest radiograph, full blood count, creatinine and urinalysis plus a high index of suspicion are the minimum; bronchoscopy confirms the diagnosis, but it is not always available, and a compatible clinical picture (haemoptysis plus new diffuse infiltrates plus falling haemoglobin plus renal involvement) is enough to start life-saving treatment.
• Where bronchoscopy is unavailable, sputum containing fresh red blood cells and high-resolution CT are useful pointers; infection must be excluded as far as possible clinically.
• Prednisolone is cheap and effective for the glucocorticoid backbone (1 mg/kg/day oral), even when plasma exchange, rituximab and cyclophosphamide are unavailable; many regimens start with what is available.
• Where plasma exchange is unavailable for anti-GBM disease, some centres use high-dose immunosuppression alone, but outcomes are worse; early referral to a centre with plasmapheresis (or haemodialysis/transfusion support) is the safer recommendation.
• Cyclophosphamide (oral tablets) is inexpensive and widely available and remains the backbone of anti-GBM and severe AAV induction; rituximab is costly and generally a second-line option.
• Cross-match, transfuse and support breathing first: these cost less than the wrong immunosuppression.

• Diffuse alveolar haemorrhage is a syndrome with a falling haemoglobin, new diffuse infiltrates and hypoxaemia; bronchoalveolar lavage is the diagnostic gold standard. ^[1]
• Think of DAH in two patterns: pulmonary capillaritis (vasculitic, usually antibody-driven) and bland haemorrhage (mechanical or clotting). ^[1]
• The pulmonary-renal group is GPA, MPA and anti-GBM disease; SLE is the other major autoimmune cause. ^[1][4]
• GPA is necrotising granulomatous vasculitis with sinonasal disease, nodules and cavities; MPA lacks granulomas and classically presents with glomerulonephritis and haemorrhage. ^[4]
• Anti-GBM disease affects 40–60% of patients with pulmonary haemorrhage; its antibody targets the α3 chain of type IV collagen shared by glomerular and alveolar basement membranes. ^[3]
• Up to 73% of lupus-associated DAH is bland haemorrhage without overt vasculitis. ^[1]
• First-line treatment differs by cause: methylprednisolone 500–1000 mg/day plus cyclophosphamide or rituximab for GPA/MPA; PLEX with cyclophosphamide for anti-GBM; pulse glucocorticoids plus cyclophosphamide or rituximab for SLE. ^[1][3][4][5]
• The 2021 ACR/Vasculitis Foundation guideline recommends against routine plasma exchange for severe GPA/MPA with alveolar haemorrhage. ^[4]
• For anti-GBM disease, PLEX continues until antibody is suppressed, typically 14 days, with plasma added in alveolar haemorrhage. ^[3]
• ANCA specificity and clinical phenotype, not antibody status alone, predict heterogeneity and outcome in severe AAV-DAH. ^[2]
• Earlier diagnosis and treatment, before oxygen or renal dependence, produce the best outcomes.

• "Vasculitis: ANCA, Behcet and medium-vessel disease" on the Chapel Hill classification, GPA/MPA/EGPA and Behcet, including complete ANCA testing.
• "Nephritic syndrome" in the renal chapter for rapidly progressive glomerulonephritis, complement patterns and renal biopsy.
• "Acute kidney injury" for the approach when renal involvement dominates.
• "Systemic lupus erythematosus" in the musculoskeletal chapter for SLE classification, hydroxychloroquine and lupus nephritis management.
• "Eosinophilic pulmonary syndromes" for EGPA as an eosinophilic vasculitic differential.
• "Chronic cough and haemoptysis" for causes of bleeding at other levels of the airway.
• "Hypoxaemia and respiratory failure" for the bedside differentiation of DAH from cardiogenic oedema and ARDS.

See front matter. Every reference above is cited at least once in the text; there is no separate references section.