Kidney dysfunction due to AA amyloidosis in a morbidly obese female.

Kidneys are commonly involved in systemic amyloidosis. Systemic AA amyloidosis is known to be associated with states of chronic inflammation such as autoimmune conditions, chronic infections, and malignancies. Obesity is increasingly recognized to be a risk factor for low-grade, chronic inflammation. We report a 48-year-old female with morbid obesity who presented with unexplained persistent mild kidney dysfunction and low-grade proteinuria. Attempt at evaluating the cause of kidney dysfunction included performing kidney biopsy despite technical challenges. Kidney biopsy showed AA amyloidosis with predominant vascular deposition, explaining the absence of nephrotic-range proteinuria. Evaluation for secondary causes of systemic AA amyloidosis was negative. While our patient was treated with sleeve gastrectomy for morbid obesity with reasonable response, it is likely that ongoing chronic inflammation, reflected by her laboratory markers, resulted in AA amyloidosis. Treatment with anakinra, an interleukin-1 antagonist, led to improvement in the laboratory markers in the next 6 months, and her kidney function remained stable. This report highlights an important cause of kidney dysfunction in morbid obesity, an atypical presentation of AA amyloidosis, and emphasizes the value of kidney biopsy in such patients.
Competing Interests: KDJ reports consultancy agreements with Secretome, George Clinicals, PMV pharmaceuticals, GSK, and Calliditas. KDJ reports honoraria from the American Society of Nephrology and UpToDate.com; reports serving on the editorial boards of American Journal of Kidney Diseases, CJASN, Clinical Kidney Journal, Journal of Onconephrology, Kidney International, and Nephrology Dialysis Transplantation; reports serving as Editor-in-Chief of ASN Kidney News and section editor for onconephrology for Nephrology Dialysis Transplantation. Figure 1Obesity-associated vascular and mesangial AA amyloidosis. Congo red staining highlights mainly vascular amyloid deposits and scant amyloid deposition in the mesangium (A) with apple-green birefringence under polarized light (B). The amyloid stained strongly with anti-SAA antibody (C). Table 1.Trend of inflammatory markers with treatment. ParameterInitial presentationAt 3 monthsAt 6 monthsC-reactive protein (mg/L)19.423.27.3Serum amyloid A protein (mg/L)26269Interleukin-6 (IU/L)493Interleukin-18 (IU/L)270254
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