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P099. Systemic AA amyloidosis associated with inflammatory bowel disease

P. Sattianayagam, S. Gibbs, J. Pinney, A. Wechalekar, H. Lachmann, P. Hawkins, J. Gillmore

National Amyloidosis Centre, London, United Kingdom

Introduction: Inflammatory bowel disease is a recognised cause of AA amyloidosis (AA), which is characterised by deposition of protein in a fibrillary conformation and consequent organ dysfunction. The AA fibril precursor protein is the acute phase reactant serum amyloid A protein (SAA), which is synthesised in the liver. Amyloid regression and improvement in amyloidotic organ function can occur with reduction of inflammation, in particular SAA concentration.

Aims and Methods: We report the natural history and outcome of AA secondary to IBD in all such patients followed between 1989 and 2010 at the United Kingdom National Amyloidosis Centre. Assessment was with serial SAP scintigraphy (a nuclear medicine technique for quantifying whole body amyloid load), and with serial SAA (normal 3 mg/l) and C-reactive protein (CRP) (normal <0.8 mg/l) levels.

Results: Twenty-two patients had Crohn's disease (CD) and 4 patients had ulcerative colitis (UC). Unlike any of the UC patients, 10 of the CD patients had suppurative disease (fistulae and abscesses). The median (range) time to diagnosis of AA from diagnosis of IBD was 16.1 (0.3–33) years. Renal amyloid and a proteinuric renal presentation was universal. At baseline, splenic, adrenal and hepatic amyloid deposits were present on SAP scintigraphy in 26, 12 and 3 cases respectively. Median time from renal dysfunction to end-stage renal failure (ESRD) by Kaplan–Meier estimate was 6.3 years. Proteinuria completely resolved and renal excretory function remained stable in 5 patients whose IBD was well controlled and hence whose median SAA levels during follow-up remained ≤12 mg/l. Despite normal serial CRP levels in 1 patient, a median SAA level of 21 mg/l indicated ongoing inflammation and he experienced progressive renal dysfunction culminating in ESRD because of ongoing amyloid formation. Renal transplantation (RTx) was undertaken in 6 patients a median (range) time of 1.7 years (0.2–7.8) from ESRD. Four grafts were functioning at censor 0.8, 3.2, 4.2 and 20.1 years after RTx. Another patient's graft was about to fail at censor because of recurrent urolithiasis 24.6 years after RTx. There was only one graft failure because of amyloid recurrence 14.5 years after RTx in the only patient who had persistently elevated SAA levels over a prolonged period after RTx.

Conclusions: AA associated with IBD is more common in CD than UC, perhaps related to the greater prevalence of suppurative features in the former. It presents with proteinuric renal dysfunction. Cases of IBD should be screened for AA with regular urine dipstick testing. Good control of the underlying inflammation (guided by SAA rather than CRP levels) can result in stabilisation or regression of amyloid and improvement in organ function. RTx is recommended in selected cases provided that inflammation is controlled.