AA amyloidosis

AA amyloidosis, also known as secondary amyloidosis, is a form of amyloidosis characterized by the accumulation of amyloid A protein in organs and tissues throughout the body. Amyloid A protein is an acute-phase reactant produced by the liver in response to inflammation. AA amyloidosis typically arises as a complication of chronic infectious or inflammatory diseases, such as rheumatoid arthritis, inflammatory bowel disease, and chronic infections.

Etiology

The development of AA amyloidosis is closely linked to chronic inflammation. Inflammatory conditions lead to sustained high levels of serum amyloid A (SAA) protein, a precursor to amyloid A. Over time, the continuous production and deposition of SAA protein fragments in tissues form amyloid deposits, impairing organ function.

Pathophysiology

In AA amyloidosis, the amyloid deposits primarily consist of fibrils derived from the cleavage of SAA protein. These fibrils disrupt the normal architecture and function of affected organs. The kidneys are most commonly involved, leading to proteinuria and potentially progressive renal failure. However, the liver, spleen, heart, and gastrointestinal tract can also be affected.

Clinical Presentation

The symptoms of AA amyloidosis are often nonspecific and vary depending on the organs involved. Common manifestations include: - Fatigue - Weight loss - Edema due to nephrotic syndrome - Hepatomegaly or splenomegaly - Cardiac arrhythmias or heart failure, if the heart is involved

Diagnosis

Diagnosis of AA amyloidosis involves a combination of clinical evaluation, laboratory tests, and histological examination. The presence of a chronic inflammatory condition, along with symptoms suggestive of organ involvement, may prompt further investigation for amyloidosis. Laboratory tests may show elevated levels of SAA protein. The definitive diagnosis is made by biopsy of an affected organ or abdominal fat pad, demonstrating amyloid deposits with specific staining properties.

Treatment

Treatment of AA amyloidosis focuses on managing the underlying inflammatory condition to reduce the production of SAA protein. This may involve the use of anti-inflammatory medications, immunosuppressants, or biologic agents. In cases where renal function is significantly impaired, dialysis or kidney transplantation may be necessary. There is also ongoing research into therapies that can directly remove amyloid deposits or inhibit their formation.

Prognosis

The prognosis of AA amyloidosis varies depending on the extent of organ involvement and the effectiveness of treatment for the underlying inflammatory condition. Early diagnosis and aggressive management of the inflammatory disease can improve outcomes and slow the progression of organ damage.

See Also

- Amyloidosis - Chronic inflammation - Nephrotic syndrome - Rheumatoid arthritis - Inflammatory bowel disease