CGRA9: A CASE OF IDIOPATHIC AA AMYLOIDOSIS

A 55-year-old man, presenting with renal failure and nephrotic range proteinuria was diagnosed with AA amyloidosis (AA on immunohistochemistry; plasma cell dyscrasia and familial amyloidosis excluded on comprehensive testing). Despite a CRP of 108 mg/L and extensive investigations, an underlying inflammatory process was not able to be identified. Serum Amyloid A (SAA) level was 108 mg/L. The patient was first trialled on prednisolone, then colchicine but a satisfactory response could not be achieved. His renal function continued to decline and he became dialysis dependant. The patient was then given a trial of anti-IL1 therapy (Anakinra). This saw significant reduction in his SAA level to 5.9 mg/L. Five years after his initial diagnosis, the patient received a renal transplant. Anakinra was discontinued with the hope the significant immunosuppression required post-transplant would also control the process driving his amyloidosis. AA amyloidosis is often thought to be a complication of inflammatory diseases as amyloid AA fibrils are derived from the acute phase reactant SAA protein. In a significant and growing proportion of cases (up to 20-25% cases), however, no underlying cause for systemic amyloidosis is found. This presents a unique therapeutic dilemma as treatment of AA amyloidosis relies on treatment of the underlying condition to reduce serum amyloid protein and there is an increasing role for the use of targeted therapies. The increasing incidence of idiopathic AA amyloidosis also raises the question about the underlying mechanism of this disease. We will explore this further in our discussion.