الفهرس 
Pathogenesis of pulmonary renal syndromeOnly 14 pages are availabe for public view
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Abstract
Pulmonary-renal syndrome is defined as the combination of diffuse alveolar haemorrhage and glomerulonephritis. Several types of immunologic injury as well as other non-immunologic mechanisms such as anti-Glomerular Basement Membrane (anti-GBM), immunocomplexes and thrombotic microangiopathy are involved in the syndrome pathogenesis.
The pulmonary lesion in the majority of cases of pulmonary-renal syndrome is small-vessel vasculitis, characterized by a destructive inflammatory process that involved arterioles, venules and alveolar capillaries (necrotic pulmonary capillaritis). These lesonis disrupt perfusion and the continuity of the pulmonary capillary wall, allowing blood to extravasate in the alveolar space. This is clinically expressed with diffuse alveolar haemorrhage.
The renal pathology in the majority of cases of pulmonary-renal syndrome is a form of focal proliferative glomerulonephritis. Fibrinoid necrosis is frequently seen, sa well as microvacular thrombi.
The term Goodpasture’s syndrome is used for the clinical entity of diffuse alveolar haemorrhage and rapidly progressive glomerulonephritis associated with anti-glomerular basement membrane antibodies.
Syndrome is extremekly rare (one case per 1,000,000 population per year). The disease predominantly affects caucasions of every age but mostly those in the second to third decades and the fifth to sixth decades of life, with a slight predominance of males. Although rare, this syndrome is responsible for about 20% of acute renal failure cases due to rapidly progressive glomerulonephritis. Both genetic and environmental factors have been implicated in the pathogenesis of Goodpasture’s syndrome.
Human anti-GBM antibodies belong mostly to the IgG class and react with a limited number of epitopes on the non-collageneous domain of the α3 chain of type IV collagen (NC1 α3 IV),a molecule expressed in the basement membranes of renal glomerulus, renal tubule, alveoli, choroids plexus, retinal capillaries and Bruchs’s membrane.
Circulating ANCA autoantibodies are detected in the majority of patients presenting with pulmonary-renal syndrome. Wegener’s disease or Wegener’s granulomatosis is characterized by the triad of systemic necrotizing vasculitis.
ANCA-negative systemic vasculitis is very rare. Porpylthiouracil and hydralazine and ANCA are detected in 20% of patients receiving propylthiouracil, but only a minority of these patients develop clinical manifestations of systemic vasculitis including pulmonary-renal syndrome.
The most frequent diagnoses in patients with pulmonary-renal syndrome admitted to the ICU are perinuclear ANCA vasculitis, followed by cytoplasmic ANCA vasculitis, Goodpasture’s syndrome, systemic lupus erythematosus and catastrophic APS. The diagnosis is already know nin the majority of those patients admitted to the ICU; the main cause of admission in these patients in infection or adverse drug effects, including severe infectious complications related to the immunosuppressive treatment. However, present with serious renal impairment and adult respiratory distress syndrome of unknown aetiology.
The possibility of a pulmonary-renal syndrome should be considered in those patients with bilateral pulmonary infiltrates in the face of the following: falling haemoglobin levels,renal failure necessitating haemodialysis, sinusitis, mononeuritis multiplex, polyarthralgia, severe asthma attack, pericarditis, cerebral ischaemia, purpura or congestive heart failure.
Haemoptysis is the most common clinical manifestation of diffuse alveolar haemorrhage. However, 30-35% of patients may have diffuse alveolar haemorrhage without evidence of haemoptysis. Breathlessness, cough and low-grade fever may also be present. The most common renal manifestation of pulmonary-renal syndrome is haematuria, protueinuria and active urinary sediment. If left untreated, patients can progress to end-stage renal failure, requiring haemodilaysis.
Chest roentgenograms and computerized tomography scanning are used to depict diffuse alveolar haemorrhage. Urinalysis reveals dysmorphic red cells of glomerular origin. Proteinuria is always present. In the vast majority of patients, bound urea nitrogen and creatinine levels are elevated, ssociated with oliguria, hypertension and oedema. A normochromic normocytic anaemia is frequently observed. The detection is serum of antibodies such as anti-GBM and/or ANCA is of major importance.
Appropriate management of such patients includes early and accurate diagnosis, exclusion of infection, close monitoring and specialized. Maintenance therapy includes low-dodse corticosteroids with cytotoxic agents. Renal transplantation remains the only alternative for patients with pulmonary renal syndrome who developed end-stage renal disease.