Pulmonary-renal syndromes or lung-kidney syndromes are clinical syndromes defined by a combination of diffuse alveolar haemorrhage (DAH) and
glomerulonephritis. Pulmonary-renal syndromes are not a single entity, but are caused by a wide variety of diseases, including various forms of primary
systemic vasculitis (especially
Wegener's granulomatosis and
microscopic polyangiitis),
Goodpasture's syndrome (associated with
autoantibodies to the alveolar and glomerular basement membrane) and
systemic lupus erythematosus. The diagnosis rests on the identification of particular patterns of clinical, radiologic, pathologic and laboratory features. Serologic testing is important in the diagnostic work-up of patients presenting with a
pulmonary-renal syndrome. The majority of cases of
pulmonary-renal syndrome are associated with ANCAs, either
c-ANCA or
p-ANCA, due to
autoantibodies against the target
antigens proteinase-3 and
myeloperoxidase respectively. The
antigen target in
Goodpasture's syndrome is
type IV collagen, the major component of basement membranes. Diffuse alveolar haemorrhage is characterized by the presence of a haemorrhagic bronchoalveolar lavage (BAL) in serial BAL samples. In the clinical setting of an acute
nephritis syndrome, percutaneous renal biopsy is commonly performed for histopathology and immunofluorescence studies. Treatment of generalized
ANCA-associated vasculitis consists of
corticosteroids and
immunosuppressive agents such as
cyclophosphamide (as induction
therapy) or
azathioprine (as maintenance
therapy once remission has been achieved). The combination of
plasmapheresis with these
cytotoxic agents and
steroids is effective in patients with
Goodpasture's syndrome, especially if instituted early in the course of the disease. Recent evidence suggests that patients with severe
ANCA-associated vasculitis, defined by the presence of diffuse alveolar haemorrhage and/or severe renal involvement (
creatinine concentration > 5.7 mg/dl), might benefit from
plasma exchange in combination with
cyclophosphamide and
corticosteroids.