Pulmonary-renal syndrome is diffuse alveolar hemorrhage plus glomerulonephritis, often occurring simultaneously. Cause is almost always an autoimmune disorder. Diagnosis is by serologic tests and sometimes lung and renal biopsy. Treatment typically includes immunosuppression with corticosteroids and cytotoxic drugs.
Pulmonary-renal syndrome is not a specific entity but is a syndrome that has a specific differential diagnosis and a specific sequence of testing.
Pulmonary pathology is small-vessel vasculitis involving arterioles, venules, and, frequently, alveolar capillaries.
Renal pathology is small-vessel vasculitis resulting in a form of focal segmental proliferative glomerulonephritis.
Etiology of Pulmonary-Renal Syndrome
Pulmonary-renal syndrome is almost always a manifestation of an underlying autoimmune disorder. Goodpasture syndrome is the prototype cause, but pulmonary-renal syndrome can also be caused by systemic lupus erythematosus, granulomatosis with polyangiitis, microscopic polyangiitis, and, less commonly, by other vasculitides, systemic rheumatic disorders, and drug-induced vasculitides (see table Causes of Pulmonary-Renal Syndrome).
Pulmonary-renal syndrome is less commonly a manifestation of immunoglobulin A (IgA)-mediated disorders, such as IgA nephropathy or IgA–associated vasculitis, and of immune complex–mediated renal disease, such as essential mixed cryoglobulinemia. Rarely, rapidly progressive glomerulonephritis alone can cause the syndrome through a mechanism involving renal failure, volume overload, and pulmonary edema with hemoptysis.
Symptoms and Signs of Pulmonary-Renal Syndrome
Symptoms and signs typically include
Cough
Dyspnea
Fever
Hematuria
Hemoptysis
Peripheral edema
Patients may also have other signs of glomerulonephritis. Pulmonary and renal manifestations can occur weeks to months apart.
Sometimes the disease has sudden flare-ups.
Pearls & Pitfalls
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Diagnosis of Pulmonary-Renal Syndrome
Serologic testing
Sometimes lung and kidney biopsies
Pulmonary-renal syndrome is suspected in patients with hemoptysis not obviously attributable to other causes (eg, pneumonia, carcinoma, bronchiectasis), particularly when hemoptysis is accompanied by diffuse parenchymal infiltrates and findings suggesting renal disease.
Initial testing includes urinalysis for evidence of hematuria and red cell casts (suggesting glomerulonephritis), serum creatinine for renal function assessment, and a complete blood count for evidence of anemia. Chest x-ray is done if not yet obtained.
Definitive diagnosis requires lung biopsy, with findings of small-vessel vasculitis, or renal biopsy, with findings of glomerulonephritis with or without antibody deposition.
Pulmonary function tests and bronchoalveolar lavage are not diagnostic but can be used to help confirm diffuse alveolar hemorrhage in patients with glomerulonephritis and pulmonary infiltrates but without hemoptysis. Lavage fluid that remains hemorrhagic after sequential sampling establishes diffuse alveolar hemorrhage, especially when hematocrit is falling.
Serum antibody testing may help distinguish some causes, as in the following:
Antiglomerular basement membrane antibodies: Goodpasture syndrome
Antibodies to double-stranded DNA and reduced serum complement levels: Systemic lupus erythematosus
Antineutrophil cytoplasmic antibodies (ANCA) to proteinase-3 (PR3-ANCA or cytoplasmic ANCA [c-ANCA]): Granulomatosis with polyangiitis
ACNA to myeloperoxidase (MPO-ANCA, or perinuclear ANCA [p-ANCA]): Microscopic polyangiitis
Treatment of Pulmonary-Renal Syndrome
Corticosteroids
Plasma exchange
Cyclophosphamide, at a dose of 0.5 to 1 g/m2cyclophosphamide; it is non-inferior and causes fewer adverse effects.
Plasma exchange is also often used, particularly in Goodpasture syndrome and certain vasculitides.
Transition to maintenance therapy may occur 6 to 12 months after the initiation of induction therapy or after clinical remission. Maintenance therapy includes low-dose corticosteroids coupled with cytotoxic agents. However, relapse may occur despite ongoing therapy.
Key Points
The most suggestive clue to pulmonary-renal syndrome is often that patients have both unexplained pulmonary and renal symptoms, even when such symptoms occur at different times.
Do routine laboratory tests (including urinalysis and chest x-ray) as well as autoantibody testing.
Confirm the diagnosis when necessary with lung or kidney biopsy.
Treat underlying autoimmune disorders.
