Goodpasture syndrome overview

# Overview
Goodpastures disease is a rare condition characterised by rapid destruction of the kidneys and the lungs. It is a type type II hypersensitivity reaction in which autoantibodies are produced against glomerular basement membrane (GBM) and alveolar basement membrane. The term Goodpasture syndrome is named after American physician Dr. Ernest William Goodpasture. There are no known direct causes for Goodpasture syndrome. However, Goodpasture syndrome must be differentiated from other diseases that cause rapid progressive glomerulonephritis and pulmonary hemorrhage. The prevalence of Goodpasture syndrome worldwide is an estimated 1 case per million individuals, with high prevalence in Caucasians. Common risk factors in the development of Goodpasture syndrome may be occupational, environmental, genetic, and viral. Symptoms of Goodpasture syndrome include, malaise, pyrexia and chills and arthralgia, fatigue, lethargy, pallor, and anorexia. Laboratory findings consistent with the diagnosis of Goodpasture syndrome include presence of autoantibodies such as  anti-glomerular basement membrane antibodies. Other diagnostic studies for Goodpasture syndrome include renal biopsy. The mainstay of therapy for Goodpasture syndrome consist of corticosteroids, cyclophosphamide and plasmapheresis.

# Historical Perspective
Goodpasture syndrome was first discovered by Dr.Ernest William Goodpasture, an American pathologist and physician, who studied the influenza pandemic in 1919, described a fatal disease that was associated with glomerulonephritis and pulmonary hemorrhage.

# Classification
There is no established system for the classification of Goodpasture syndrome.

# Pathophysiology
The pathogenesis of Goodpasture syndrome includes the presence of autoantibodies directed against the glomerular or alveolar basement membrane. As with many autoimmune conditions, the precise cause of Goodpastures Syndrome is not yet known. It is believed to be a type II hypersensitivity reaction to Goodpastures antigens on the cells of the glomeruli of the kidneys and the pulmonary alveoli, specifically the basement membrane's (including a-3 chain of type IV collagen), whereby the immune system wrongly recognizes these cells as foreign and attacks and destroys them, as it would an invading pathogen. The target antigen that has the strongest pathogenic effect on anti-GBM disease is the non-collagenous 1 domain of alpha-3 type IV collagen. There is strong correlation of anti-glomerular basement membrane disease with allele HLA DRB1-1501. This allele is associated in causing renal injury. On gross pathology, Goodpasture syndrome with lung involvement may present with diffuse pulmonary hemorrhage. On microscopic histopathological analysis, early focal proliferative changes that display necrosis and crescent formation with an inflamed interstitial are seen. Under direct immunofluorescence,  linear immunoglobulin G deposits are found encompassing the glomerular basement membrane and at times the distal tubular portion of the basement membrane.

# Causes
There are no known direct causes for Goodpasture syndrome. Common risk factors for Goodpasture syndrome are viral or bacterial infections and certain environmental and behavioral risk factors such as smoking, hydrocarbons, formaldehyde and cocaine use.

# Differentiating Goodpasture syndrome from Other Diseases
Goodpasture syndrome must be differentiated from other diseases that cause rapid progressive glomerulonephritis and pulmonary hemorrhage. ANCA associated vasculitis, are disorders that affect the renal and pulmonary system, must be differentiated from Goodpasture syndrome.

# Epidemiology and Demographics
The prevalence of Goodpasture syndrome worldwide is an estimated 1 case per million individuals, with high prevalence in Caucasians. The peak incidence of the disease occurs between the ages of 20 and 30 and again at 60 and 70. Goodpasture syndrome affects men and women equally.

# Risk Factors
Common risk factors in the development of Goodpasture syndrome may be occupational, environmental, genetic, and viral. However, we don't known what causes the antibodies to form.

# Screening
There is insufficient evidence to recommend routine screening for Goodpasture syndrome.

# Natural History, Complications, and Prognosis
If left untreated, Goodpasture syndrome can progress to end stage renal disease and pulmonary failure. Complications of Goodpasture syndrome include, infections, alveolar hemorrhage, end stage renal disease, and pulmonary failure. The prognosis of Goodpasture syndrome is variable, as it depends upon the diagnosis, start of treatment and the level of serum creatinine.

# Diagnosis

## History and Symptoms
Obtaining a complete history is an important aspect of making a diagnosis of Goodpasture syndrome, as it can provide insight into cause, precipitating factors, and associated underlying conditions. Symptoms may develop acutely or rapidly affecting the renal and pulmonary system. Symptoms of Goodpasture syndrome include, malaise, pyrexia and chills and arthralgia, fatigue, lethargy, pallor, and anorexia.

## Physical Examination
A complete medical history and comprehensive renal and pulmonary exam must be performed to help identify and properly diagnose Goodpasture syndrome.The presence of tachypnea, inspiratory crackles, edema and hypertension on physical examination are suggestive of presence of renal and pulmonary disorders such as Goodpasture syndrome.

## Laboratory Findings
Laboratory findings consistent with the diagnosis of Goodpasture syndrome include presence of autoantibodies such as anti-glomerular basement membrane antibodies. Other findings associated with pulmonary and renal injury include elevated blood urea nitrogen, low-grade proteinuria, gross or microscopic hematuria, and red cell casts.

## X-ray
On chest X-ray, Goodpasture syndrome is characterized by parenchymal consolidations that are most often present in both lungs, perihilar, and bibasilar. When pulmonary hemorrhage is recurrent an interstitial pattern is observed.

## Echocardiography
There are no echocardiography findings associated with Goodpasture syndrome.

## CT scan
CT scan of the thorax may be helpful in the diagnosis of Goodpasture syndrome. Findings on CT scan suggestive of Goodpasture syndrome include parenchymal consolidation, ground glass appearance that may progress to reticular pattern and interlobular septal thickening in later stage of disease.

## Other Diagnostic Studies
Other diagnostic studies for Goodpasture syndrome include renal biopsy. In patients with inconclusive lab and imaging findings, renal biopsy remains the gold standard in establishing the presence of Goodpasture syndrome. A renal biopsy can also identify the severity of disease and guide medical therapy.

# Treatment

## Medical Therapy
Currently there is no cure for Goodpasture syndrome.The mainstay of therapy for Goodpasture syndrome consist of corticosteroids, cyclophosphamide and plasmapheresis.

## Surgery
Surgery is not the first-line treatment option for patients with Goodpasture syndrome. Renal transplantation is usually reserved for patients who present with undetectable circulating anti-glomerular basement antibodies in serum for 12 months and atleast 6 months after stopping the use of cytotoxic agents.

## Secondary Prevention
Effective measures for the secondary prevention of Goodpasture syndrome include patient education. Patients should be educated about the signs and symptoms of renal dysfunction as certain steroid and immunosuppressive therapy may have adverse effects on the kidneys. Patients should be monitored regularly for renal function and those with severe dysfunction should have be referred for dialysis.