Critical Care Medicine

Diffuse Alveolar Hemorrhage, Pulmonary capillaritis

Diffuse alveolar hemorrhage

Also known as: Pulmonary capillaritis

Related conditions: Anti-glomerular membrane antibody disease (Goodpasture's), microscopic polyangiitis, granulomatous polyangiitis (Wegener's), idiopathic pulmonary hemosiderosis, pulmonary-renal syndromes

1. Description of the problem

Diffuse alveolar hemorrhage (DAH) occurs in a number of immune-mediated disorders, but can also occur in non-immune conditions. Severe DAH can lead to acute respiratory failure and death. Prompt recognition is crucial so that effective therapy is begun as soon as possible.

The classic triad of DAH is hemoptysis, bilateral alveolar infiltrates on chest x-ray, and anemia.

Hemoptysis varies in amount and may be absent, even with life-threatening DAH. Massive hemoptysis is uncommon. Severe DAH with minimal (or no) hemoptysis is explained by the diffuse capillary origin of bleeding. X-rays most often show bilateral alveolar infiltrates, but asymmetry is not unusual. Unilateral DAH is rare. The radiographic pattern is not readily distinguishable from other alveolar filling processes.

Anemia results from blood loss into the lung. Hemoglobin decrement of several grams/dL in 24 hours is common with severe DAH. Repeated DAH can lead to iron deficiency anemia.

Immune-mediated DAH is due in the vast majority of cases to an underlying pulmonary capillaritis, with neutrophil infiltration and fibrinoid necrosis of alveolar walls leading to the widespread extravasation of erythrocytes into air spaces. Involvement of vessels larger than venules or arterioles is rarely observed. The underlying pathology is analagous to cutaneous leukocytoclastic vasculitis.

In most cases, immune-mediated DAH is accompanied by extrapulmonary manifestations of the underlying disease. By far the most common extrapulmonary feature is acute glomerulonephritis (GN), and the presence of DAH with GN is sometimes referred to as the pulmonary-renal syndrome.

The three major categories of the pulmonary-renal syndrome (DAH with GN) are 1) antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, 2) anti-glomerular basement membrane antibody (AGBMA) disease (Goodpasture's syndrome), and systemic lupus erythematosus (SLE).

Isolated DAH (without GN or other extrapulmonary features) can occur in both ANCA and AGBMA-mediated disorders, but is uncommon and is typically soon followed by evolution of multisystem disease. Pulmonary capillaritis with DAH can also occur in the absence of any measurable pathologic antibodies in serum. Isolated seronegative pulmonary capillaritis is considered to be a lung-limited small-vessel vasculitis, but its pathogenesis is unknown. Isolated DAH has also been described without demonstrable capillaritis, in which case the term "idiopathic pulmonary hemosiderosis" is often applied.

Although DAH is usually a manifestation of an underlying immune disorder, it is important to recognize that there are non-immune causes of DAH. Some non-immune causes of DAH include a marked increase in pulmonary capillary pressure (eg, mitral stenosis, acute mitral insufficiency), drugs or toxins (eg, cocaine), pneumonia (eg, Panton-Valentine leukocidin-producing Staphylococcus aureus, invasive aspergillus, leptospirosis), severe coagulopathies, and bone marrow or stem cell transplant.

It is crucial that non-immune DAH not be mistaken for an immune-mediated disorder since the latter disorders are often treated with intensive immunosuppression.

2. Emergency Management

Severe DAH can rapidly lead to fulminant hypoxemic respiratory failure and may be fatal. The most important aspect of initial assessment is to determine the need for intubation and mechanical ventilatory support because of established or impending respiratory failure. Simultaneously, empiric treatment directed at arresting ongoing lung hemorrhage should be begun, even before a definitive diagnosis is established.

Management of respiratory failure

The most immediate life-threatening complication of DAH is acute hypoxemic respiratory failure. Nearly all patients will need supplemental oxygen and many will require intubation and mechanical ventilation. When severe DAH results in the adult respiratory distress syndrome (ARDS), high levels of FI02 and positive end-expiratory pressure (PEEP) are often needed to achieve acceptable oxygenation. Low tidal volume ventilation (~6 mL/kg/ideal body weight) is recommended, keeping the plateau pressure below 30 cm H2O if possible.

Permissive hypercapnia may be necessary in some cases, especially when a markedly decreased lung compliance and need for high-level PEEP dictate further reduction in tidal volume. Patients who have acute GN may have inadequate metabolic compensation for respiratory acidosis. In such cases, correction of the mixed respiratory and metabolic acidosis is as a rule more safely accomplished by dialysis than by increasing tidal volume to levels that produce lung overdistention.

It is uncertain whether high-level PEEP (eg, ≥15 cm H2O) directly reduces the severity of bleeding, but anecdotal evidence with DAH in leptospirosis suggests that this may be true in some cases.

For patients with refractory hypoxemia, options include the use of inhalednitric oxide or aerosolized prostacyclin, prone positioning or high-frequency oscillatory ventilation. If these measures are unsuccessful, use of extracorporeal life support (ECLS) should be considered. Given that the fundamental underlying problem is massive bleeding into the lung, a potential limiting factor of ECLS is the anticoagulation that is usually given to prevent thrombosis in the extracorporeal system.

Nonetheless, there have been reports of successful application of ECLS with therapeutic anticoagulation for severe DAH. Furthermore, the newer rotary pumps and membranes are much less thrombogenic and ECLS can sometimes be used successfully without anticoagulation. Given that immune-mediated DAH is often a fully reversible cause of respiratory failure, and that improvement sometimes occurs within a few days, a trial of ECLS for fulminant DAH with refractory hypoxemia is fully justifiable.

In those few instances in which DAH is accompanied by large amounts of hemoptysis, the latter may result in endobronchial clots that obstruct the airway. This should be considered if lung auscultation reveals diminished breath sounds or the chest x-ray shows atelectasis. If there is any doubt about endobronchial clots with airway obstruction, early fiberoptic bronchoscopy should be performed.

It is important to recognize that on rare occasions blood clots may lodge in the endotracheal tube, leading to a sudden increase in airway pressure and rapid clinical deterioration. If the clot cannot be immediately dislodged, removal of the obstructed tube with reintubation may be life-saving.

Since most cases of otherwise unexplained severe DAH will ultimately be shown to have an immune etiology, empiric treatment with high-dose corticosteroids (pulse methylprednisolone, 1g intravenously) is recommended while efforts are underway to clarify the underlying diagnosis. Even if the subsequent workup defines a non-immune cause of DAH, it is unlikely that short-term use of corticosteroids will be harmful.

Unfortunately, corticosteroid therapy is sometimes withheld from patients with DAH until a definitive diagnosis is made, increasing the likelihood of progression to the point of respiratory failure or even death.

Plasmapheresis is recommended for all patients with AGBMA disease and for those with ANCA-associated vasculitis who have severe DAH. Ideally, confirmation of the underlying diagnosis by measurement of serum ANCA and AGBMA would precede use of plasmapheresis. However, it is not always possible to obtain results of these assays rapidly. Given that ANCA and AGBMA account for the majority of cases of immune DAH, it is reasonable to initiate plasmapheresis before serology is completed in the setting of life-threatening DAH.

If serologic studies end up showing neither ANCA nor AGBMA there is less rationale for continuing daily plasma exchange.

Initial management of severe DAH: key points

Initial management of patients with potentially life-threatening DAH should include the following:

1) Measurement of O2 saturation, arterial blood gases, and clinical evaluation of work of breathing to assess adequacy of gas exchange and need for mechanical ventilatory support

2) If intubated, use of low tidal volume ventilation (~6mL/kg/ideal body weight) and PEEP as needed to achieve acceptable oxygenation

3) Standard measures used for refractory hypoxemia in ARDS (eg, inhaled NO or prostacyclin, prone position, high frequency oscillatory ventilation) are also appropriate for severe DAH. In addition, ECLS should be considered for patients who do not respond to the above approaches.

4) Administration of pulse methylprednisone (1g IV) unless a non-immune cause of DAH is immediately apparent. Plasmapheresis is indicated for proven AGBMA disease and for severe ANCA-associated DAH, but should also be considered for patients with life-threatening DAH pending serologic confirmation of the underlying disorder.

3. Diagnosis

There are three basic steps in approaching a diagnosis of DAH: 1) confirming that the cause of the clinical and radiographic picture of dyspnea, hypoxemia, and radiographic infiltrates is indeed due to diffuse microvascular lung hemorrhage, 2) excluding non-immune causes of DAH, 3) establishing the immune disorder in those patients with immune-mediated DAH.

Establishing the presence of DAH and excluding possible non-immune etiologies

The first step in approaching the patient with suspected DAH is to be certain that widespread microvascular hemorrhage is responsible for the presenting clinical and radiographic features.

The most important laboratory and x-ray studies that are used to evaluate possible DAH are the hemoglobin, creatinine, urinalysis, and chest radiograph. The hemoglobin will almost always be decreased, and severe anemia may be noted. Since most patients with immune DAH have concomitant GN, an elevated creatinine and/or abnormal urinalysis showing microscopic hematuria are common. Although red blood cell casts may not be apparent, if present they establish an unequivocal diagnosis of GN.

The chest x-ray in DAH usually shows air-space disease that is almost always bilateral, but may be somewhat asymmetric. In fulminant cases the x-ray is indistinguishable from severe pulmonary edema or ARDS (Figure 1). Air bronchograms may be seen on chest x-ray and are often better appreciated on CT. In less severe cases, a more patchy distribution may be seen. In the latter instance, CT may be particularly helpful in that it may reveal bilateral ground-glass opacities that are not well seen on routine x-rays (Figure 2).

Figure 1.

Chest x-ray in DAH showing bilateral air-space disease.

Figure 2.

CT scan revealing bilateral ground-glass opacities.

In some cases the presentation is so characteristic as to be diagnostic on clinical grounds. An example would be a patient who presents with the classic triad of hemoptysis, bilateral airspace opacities on chest x-ray, significant anemia and unequivocal evidence for either GN or cutaneous leukocytoclastic vasculitis.

When a clinical diagnosis of DAH is less certain, bronchoscopy with bronchoalveolar lavage (BAL) is the most useful confirmatory test. With severe DAH, fresh blood may be seen welling up from numerous segments of the lung. In less fulminant cases, the diagnosis is confirmed by return of lavage fluid that may become progressively more bloody with sequential aliquots. With subacute and chronic DAH, the BAL return may not appear grossly bloody, but cytology preparations will reveal abundant hemosiderin-laden macrophages.

The BAL fluid should be sent for routine cultures to exclude an infectious etiology for intrapulmonary hemorrhage.

Another diagnostic test for DAH is a markedly elevated diffusing capacity for carbon monoxide. Abundant fresh blood in alveoli will bind the inhaled carbon monoxide, accounting for the higher-than-expected values. However, this diagnostic approach is impractical for patients with moderate to severe DAH and is seldom used in practice.

Once DAH is confirmed, it is important to determine the underlying disorder since the approach to definitive therapy will vary. In the absence of unequivocal extrapulmonary features that define an immune-mediated disorder (ie, clear-cut evidence of GN, cutaneous vasculitis), it is important that non-immune causes of DAH be excluded. The clinical setting in which DAH occurs may be diagnostic, eg, bone marrow transplant or onset after a profound neurologic insult (seizures, head trauma, subarachnoid hemorrhage) that leads to a "blast injury" to the lung.

When the clinical setting does not provide a clear etiology, additional screening tests to evaluate for non-immune causes of DAH should include an echocardiogram (severe mitral valve disease), coagulation profile, and urine drug screen (cocaine). Although uncommon, severe DAH can result from certain infections, most notably necrotizing pneumonia caused by the Panton-Valentine leukocidin-producing strain of S aureus, invasive aspergillosis, or leptosporosis (in endemic areas).

Hemorrhagic pneumonia due to S aureus is a fulminant (and often rapidly fatal) disorder characterized by profound septic shock and multiorgan failure. Invasive aspergillosis nearly always occurs in the setting of significant immune suppression (profound neutropenia, solid organ or bone marrow transplant, prolonged corticosteroid therapy). The clinical setting and culture of blood, sputum, and BAL are essential for identifying an infectious etiology of DAH.

Establishing the cause of immune-mediated DAH

Most cases of severe DAH have an immune basis, and identification of the underlying immune disorder is based on a combination of clinical examination, routine laboratory studies to detect underlying GN, and especially serologic evaluation for ANCA, AGBMA, and ANA.

The majority of patients with immune DAH will have concomitant GN. GN occurs in ANCA-associated vasculitis, AGBMA disease, and SLE, but its presence excludes lung-limited seronegative pulmonary capillaritis and idiopathic pulmonary hemosiderosis. Isolated DAH can occur with ANCA-associated vasculitis and anti-GBM disease but is uncommon.

AGBMA disease is limited to the lungs and kidneys, while ANCA-associated vasculitis and SLE may have multisystem involvement. Therefore, clinical findings of palpable purpura, synovitis, mononeuritis multiplex, or serositis strongly favor ANCA-associated vasculitis or SLE over AGBMA disease as the underlying immune disorder.

Serology is crucial to establishing the specific immune disorder responsible for DAH. The three serologic studies that should be obtained initially are ANCA, AGBMA, and ANA. The results of these studies, together with clinical examination and laboratory evaluation for GN, will allow a simple and reliable diagnosis of immune DAH in the majority of cases.

The most common cause of immune DAH is ANCA-associated vasculitis. ANCA-associated DAH occurs in both microscopic polyangiitis (MPA) and granulomatous polyangiitis (GPA) (Wegener's). Patients with vasculitis-related DAH can have either a c-ANCA (cytoplasmic) or p-ANCA (perinuclear) immunofluorescent pattern, but not both. The c-ANCA pattern is almost always due to antiproteinase-3 antibody (by ELISA).

Therefore, a positive c-ANCA in the setting of a clear-cut clinical picture of DAH does not necessarily require further evaluation with ELISA.There is a strong association with c-ANCA and GPA (Wegener's). The p-ANCA pattern is due to antimyeloperoxidase antibody (anti-MPO) in patients with underlying MPA, but p-ANCA can also be due to other antibodies that are unrelated to vasculitis. As such, a p-ANCA should routinely be further investigated by obtaining an ELISA for anti-MPO.

The specificity of both c-ANCA (antiproteinase 3) and anti-MPO for vasculitis is very high (>90%). When assessed in the context of a strongly suggestive clinical picture for vasculitis (eg, DAH, GN, cutaneous leukocytoclastic vasculitis), a strongly positive value for either c-ANCA or anti-MPO has a very high positive predictive value for defining underlying ANCA-associated vasculitis and for practical purposes can be relied upon to firmly establish a diagnosis.

However, a positive result in a clinical setting with a low pretest likelihood for vasculitis (eg, simple hemoptysis, nonspecific pulmonary infiltrates) may well represent a false positive. As useful as the serum ANCA can be in the evaluation of patients with suspected vasculitis, it cannot be overemphasized that a positive test must always be interpreted in light of the clinical presentation.

As noted above, ANCA-associated DAH may be further classified as MPA or GPA (Wegener's). Differentiation of these two conditions is based upon both the clinical and radiographic features. Patients with ANCA-associated DAH who also have upper airways pathology (sinus disease, nasal lesions, otitis media), cavitary lung lesions, or tracheobronchial disease almost certainly have GPA, and the great majority will have a c-ANCA pattern.

In contrast, patients with MPA are most often p-ANCA (anti-MPO) positive and have clinical and radiographic features that result solely from small vessel vasculitis (eg, DAH, GN, palpable purpura). It is uncertain whether patients with c-ANCA-positive DAH without clearly defined upper airway or cavitary lung lesions should be classified as MPA or GPA. However, from a practical standpoint, it makes little difference since the initial approach to therapy is similar (see below).

With widespread availability of serum ANCA assays, patients with vasculitis-related DAH seldom undergo tissue biopsy. The lung pathology of ANCA-associated DAH is a pauci-immune (few or no immune deposits) pulmonary capillaritis, while the renal lesion is a pauci-immune necrotizing GN, sometimes with crescent formation. The lung and renal histopathology in ANCA-associated DAH and GN is not readily distinguishable from that seen in AGBMA and SLE, with differentiation being made on the basis of immunofluorescence (see below).

AGBMA disease (Goodpasture's) is a less common cause of immune-mediated DAH than ANCA-associated vasculitis. Patients with AGBMA-associated DAH have concomitant GN in the great majority of cases, although isolated DAH is occasionally seen at initial presentation. Diagnosis is made most conveniently by detecting serum AGBMA by ELISA. Both the sensitivity and specificity of ELISA are excellent (>90%). Therefore, a positive serum AGBMA in a patient with clear clinical evidence for DAH is diagnostic.

Another method of diagnosis is kidney biopsy, with the pathognomonic linear deposition of IgG within glomeruli. Lung biopsy is rarely indicated, but if performed may reveal pulmonary capillaritis and the same linear immunofluorescent pattern seen in the kidneys.

Another cause of immune DAH is SLE. DAH usually oocurs in patients with established SLE, and in the few cases in which it is a presenting feature it typically occurs with concomitant GN and sometimes with additional extrapulmonary/extrarenal manifestation (eg, synovitis, serositis, cutaneous lesion, etc). Serology will reveal a positive ANA. In addition, patients with SLE-related DAH and GN will usually have low serum complement levels, a laboratory finding not expected in ANCA-associated vasculitis or AGBMA disease.

If renal biopsy is performed in patients with SLE, the histopathology may be similar to that seen with ANCA and AGBMA, but is distingushed by the presence of granular ("lumpy-bumpy") immunofluorescence as a result of immune complex deposits in glomeruli. Though rarely perfomed, lung biopsy in SLE-related DAH would be expected to reveal capillaritis with a similar immunofluorescent pattern as that found in the kidney.

Although uncommon, DAH may also occur in primary antiphospholipid antibody syndrome. When the clinical and serologic studies (ANCA, AGBMA, ANA) do not provide a clear diagnosis of the disease reponsible for DAH, serum antiphospholipid antibody should be measured.

In some cases, DAH occurs without clinical evidence of extrapulmonary disease and a completely negative serologic workup. When patients with isolated seronegative DAH undergo lung biopsy, some will be found to have paucimmune pulmonary capillaritis. Others may only have bland hemorrhage, in which case the term "idiopathic pulmonary hemosiderosis" is usually applied.

How to recognize that the patient has DAH

As noted earlier, the clinician can often make a confident diagnosis of DAH on clinical grounds when the presentation is classic: hemoptysis, bilateral air space opacities, anemia, and clear evidence for either GN or cutaneous leukocytoclastic vasculitis (palpable purpura). When the diagnosis is less certain, bronchoscopy with BAL is the most helpful diagnostic method.

Differential diagnosis

Some diseases that may be confused with immune DAH include hemorrhagic pulmonary edema from a markedly elevated pulmonary venous pressure (mitral stenosis or acute mitral insufficiency), necrotizing pneumonias (S aureus, aspergillosis, leptopspirosis), focal massive bleeding with secondary aspiration (malignancy, tuberculosis, bronchiectasis), and cocaine-induced lung hemorrhage.

DAH also occurs as a complication of bone marrow or stem cell transplant, in which case the clinical setting is crucial for diagnosis. Useful tests for excluding non-immune causes of DAH include a careful history and clinical examination, echocardiography, bronchoscopy with visual inspection of the airways and culture of BAL, coagulation studies, and urine drug screen.

Confirmatory tests

Confirmation of immune-mediated DAH is most easily accomplished by a combination of clinical evaluation and serology (ANCA, AGBMA, ANA); renal biopsy may also be helpful in patients with GN. Open lung biopsy is usually reserved for patients with isolated DAH who have negative serology and no convincing evidence for an alternative non-immune mechanism for DAH.

4. Specific Treatment

Cortiocosteroids are an essential component of the therapy of immune DAH, regardless of the underlying disorder. Unfortunately, there are no good data that clarify the optimal dose of corticosteroids. Pulse methylprednisolone (1g/day for 3 days) is generally recommended for all patients with known or suspected immune DAH, after which a dose of 2mg/kg/day for 1 week and prednisone 60mg/day for an additional 1 to 2 weeks would seem to be a reasonable approach.

Subsequent tapering will be dictated by the balance between risk of relapse vs risk of corticosteroid-related complications. There is no clear evidence that prolonged use of high-dose prednisone long after DAH has resolved is necessary, and the latter approach increases the risk of opportunistic infection, especially if other immunosuppression has been given.

It would seem appropriate to target a prednisone dose of 20mg/day by 4 weeks after clinical and radiographic evidence of DAH has subsided, with subsequent lowering to 10mg a day. Prophylaxis against Pneumocystis should be given when additional immunosuppression is given or when the prednisone dose remains at 20mg/day for more than 1 month.

Daily plasma exchange is a crucial intervention for DAH related to AGBMA, and should also be used for severe ANCA-related DAH. For both ANCA-associated vasculitis and AGBMA disease, the rationale for using plasma exchange is to rapidly remove pathogenic antibody. The role of plasma exchange for other causes of immune DAH is less certain.

Recommended therapy for patients with AGBMA also includes use of daily cyclophosphamide (2mg/kg/day) to prevent resynthesis of the pathogenic antibody after its removal. Therefore, AGBMA disease is treated with a combination of corticosteroids, cyclophosphamide, and plasma exchange.

Cyclophosphamide has also been standard therapy for ANCA-associated vasculitis. Recent data have shown that outcomes may be similar if rituximab is substituted for cyclophosphamide and may be associated with fewer adverse effects. Rituximab may be especially attractive for patients in their child-bearing years because of the potential for sterility with cyclophosphamide.

When rituximab is used to induce a remission of ANCA-associated vasculitis, it is given weekly in a dose of 375mg per square meter of body surface area per week for 4 weeks. The patient is then followed every 2 to 3 months to assess for recovery of B cells and ANCA. The duration of remission is not easily predicted, but once it occurs, 2 cycles of weekly rituximab are repeated to reinduce remission.

Rituximab has also been used anecdotally for DAH in AGBMA disease and for APL-related DAH that proved refractory to other interventions.

Patients with SLE-related DAH should receive corticosteroids, and if they have active GN, as is usually the case, cyclophosphamide should also be given. Reports describing use of plasma exchange and rituximab for life-threatening, refractory SLE have been published.

Patients with isolated seronegative DAH should be given corticosteroids initially (according to the dosing recommendations mentioned above), but if DAH does not respond well or recurs on corticosteroids, then cyclophosphamide should be added.

5. Disease monitoring, follow-up and disposition

Patients with immune DAH must be followed closely in order to assess the activity of the underlying immune disorder and to monitor for evidence of side effects from immunosuppressive therapy.

Patients with AGBMA who go into complete remission and who have persistently negative serology for AGBMA after 6 to 12 months of observation have an excellent prognosis since recurrence is rare.

The prognosis for long-term preservation of renal function in Goodpasture's syndrome is greatly dependent on the degree of renal impairment at presentation. If the patient has nonoliguric acute kidney injury and does not require dialysis, the long-term outcome is excellent. Conversely, advanced oliguric renal failure requiring dialysis seldom reverses.

The course of ANCA-associated vasculitis differs from Goodpasture's syndrome in a couple of key respects. First, patients who require dialysis initially may recover renal function with immunosuppressive therapy. Second, late relapse is common after induction of a complete remission and may require retreatment. Similarly, SLE is typically a chronic disease with a tendency for relapse. The course of seronegative isolated DAH is not well defined, but anecdotal experience would suggest that relapse is common and in some cases there may be months to years between relapses.

In brief, only Goodpasture's syndrome has a limited duration of disease activity, and patients with the other causes of immune DAH are at risk for delayed relapse.

Pathophysiology

The pathogenesis of most causes of immune DAH is incompletely understood. It is well accepted, however, that AGBMA plays a causative role in DAH and GN. Of interest, about one third of patients with circulating AGBMA will have only GN. It is postulated that DAH occurs when some additional factor increases the permeability of pulmonary capillaries, allowing antibody to deposit on alveolar basement membrane. Both cigarette smoking and viral infection have been proposed as possible triggers.

The pathogenetic role of ANCA has been somewhat less certain, but most investigators now believe that ANCA is indeed important in causing microvascular injury. A pathogenic role of ANCA provides a key rationale for plasma exchange in patients with severe ANCA-associated DAH. In addition, the ability to induce complete clinical remission with rituximab-induced elimination of serum ANCA provides further support for the antibody's importance in causing organ damage.

Special considerations for nursing and allied health professionals.

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What's the evidence?

Lara, AR, Schwarz, MI. "Diffuse alveolar hemorrhage". Chest. 2010. pp. 1164-1171.

(A recent concise review of DAH.)

Stone, JH, Merkel, PA, Spiera, R. "Rituximab versus cyclophosphamide for ANCA-associated vasculitis". N Engl J Med. vol. 363. 2010. pp. 221-232.

(A multicenter randomized trial showing noninferiority of rituximab for treatment of ANCA-associated vasculitis.)

Khan, SA, Subla, MR, Behl, D. "Outcome of patients with small vessel vasculitis admitted to the medical ICU". Chest. vol. 131. 2007. pp. 972-6.

(Experience of a single center (Mayo Clinic); DAH is the most common reason for ICU admission.)

Levy, JB, Turner, AN, Rees, AJ, Pusey, CD. "Long-term outcome of antiglomerular basement membrane antibody disease treated with plasma exchange and immunosuppression". Ann Intern Med. vol. 134. 2001. pp. 1033-1042.

(Large experience with Goodpasture's syndrome from a referral center in the UK.)

Zamora, MR, Warner, ML, Yuder, R, Schwarz, MI. "Diffuse alveolar hemorrhage and systemic lupus erythematosus. Clinical presentation, histology, survival, and outcome". Medicine. vol. 76. pp. 192-202.

(Experience from single center [U Colorado] with SLE-related DAH.

Gomez-Puerta, JA, Hernandez-Rodriquez, J, Lopez-Soto, A. "Respiratory disease and antineutrophil cytoplasmic antibody associated vasculitides". Chest. 2009. pp. 1101-11.

(Review of respiratory manifestations of ANCA-associated vasculitis.)

Jennings, CA, King, TE, Tuder, R. "Diffuse alveolar hemorrhage with underlying isolated, pauciimmune pulmonary capillaritis". Medicine. vol. 76. 1997. pp. 192-202.

(Description of isolated DAH with negative serology.)
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