What causes AA (inflammatory) amyloidosis?

Updated: Jan 08, 2021
  • Author: Jefferson R Roberts, MD; Chief Editor: Herbert S Diamond, MD  more...
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Answer

A wide range of infectious and noninfectious diseases, hereditary periodic fevers, and neoplasms have been associated with AA amyloidosis. [11] Chronic infectious diseases that have been associated with AA amyloidosis include the following:

The precise frequencies of AA amyloidosis in those disorders are difficult to ascertain, but they may be as high as 10% in some chronic suppurative disorders (eg, osteomyelitis). The overall incidence in autopsies in Western countries is estimated at 0.5-0.86%, where the most frequent underlying diseases are RA (23-51%), juvenile idiopathic arthritis (7-48%), and AS (0-12%). [13, 14]

RA is the most common rheumatic cause of AA amyloidosis. However, most patients with RA do not have development of AA amyloidosis. Prolonged duration of disease, continuous disease activity, and inadequate treatment are risk factors for AA amyloidosis. Renal failure due to amyloid deposition usually occurs in the fifth decade of life. In living patients with RA, the incidence of AA found on biopsies ranges from 7-29%.

In industrialized countries, chronic noninfectious inflammatory diseases are more commonly the cause of AA amyloidosis. In RA, the incidence is 5-26%, being found more often on autopsy than biopsy. The frequency of AA amyloidosis may be lower in patients treated earlier and more aggressively.

Other inflammatory disorders associated with AA amyloidosis include the following:

The most common cause of renal involvement in ankylosing spondylitis is AA amyloidosis (62%), followed by IgA nephropathy (30%). [5]

AA amyloidosis is a rare complication of inflammatory bowel disease and occurs more commonly in Crohn disease and in males. The reason that Crohn disease is more readily complicated by AA amyloidosis than ulcerative colitis is not known but may be secondary to greater degree of sustained inflammation in association with the former and, in particular, the suppurative features of Crohn disease such as abscesses and fistulae may be risk factors. [16]

Chronic juvenile arthritis seems to be a special case, with a large geographic variance (7-48%) in the incidence of AA amyloidosis depending on whether the analysis was performed in the United States (low) or Eastern Europe (high).

In the 1980s, a high frequency of renal AA amyloidosis was observed among subcutaneous drug abusers in some cities in the United States. Whether this was related to the drug or to some contaminating substance that elicited chronic inflammation when injected subcutaneously is not clear. More recently, AA amyloidosis associated with subcutaneous drug abuse was reported in 24 patients seen at a San Francisco hospital from 1998 to 2013. [17]

Familial Mediterranean fever (FMF) is characterized by recurrent attacks of fever, arthritis, pleuritis, peritonitis, or erysipelas like erythema lasting 24–48 hours. FMF begins in childhood and usually affects persons of Mediterranean origin. AA amyloidosis develops in up to one-quarter of patients with FMF. Renal AA amyloidosis is virtually a universal complication of FMF in some populations if the patients are not compliant with colchicine prophylaxis.

Other hereditary fever syndromes that may be complicated by AA amyloidosis include the following:

  • Tumor necrosis factor receptor–associated periodic syndrome (TRAPS)
  • Chronic infantile neurologic cutaneous articular syndrome (CINCA)
  • Muckle-Wells syndrome
  • Hyperimmunoglobulinemia D with periodic fever syndrome (HIDS)

Among tumors, hypernephroma has been associated with AA amyloidosis. More recently, Castleman disease (angiofollicular lymph node hyperplasia) has been recognized as a cause of amyloidosis. Resection of the tumor can lead to the regression of clinical signs of amyloid nephropathy. [18, 19]

Among other noninfectious chronic inflammatory diseases, AA amyloidosis has been reported in systemic lupus erythematosuspolymyositis, and polymyalgia rheumatica and has been observed in temporal artery biopsy samples of such patients. AA amyloidosis has also been noted in patients with gout, pseudogout, and some cases of apparently noninflammatory sarcoidosis.

 Because SAA production is mediated through inflammatory cytokines, primarily IL-6, AA deposition has been noted in other disorders associated with increased IL-6 production. Occasionally, patients with atrial myxomas, renal cell carcinomas, Hodgkin lymphoma, hairy cell leukemia, and carcinomas of the lung and stomach have been found to have renal AA amyloidosis, presumably because of production of the cytokine by the tumor cells. Paradoxically, some patients with agammaglobulinemia also have developed AA amyloidosis, demonstrating the dissociation between cytokine production and the synthesis of its normal downstream effector molecules, immunoglobulins.

Few case reports have described patients with cyclic neutropenia developing AA amyloidosis. [21]

As many as 6% of patients with AA amyloidosis have no clinically overt inflammatory disease.


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