Renal AA amyloidosis in a patient with Bence Jones proteinuria and ankylosing spondylitis.

A patient with a 10 year history of monoclonal gammopathy of undetermined significance and Bence Jones proteinuria, and a 44 year history of ankylosing spondylitis, developed a nephrotic syndrome secondary to renal amyloidosis. Clinically the amyloidosis was ascribed to Bence Jones proteinuria rather than to the burnt out ankylosing spondylitis. However, histochemical and immunofluorescence staining techniques used to type the amyloid fibrils showed AA amyloidosis, implicating ankylosing spondylitis rather than monoclonal gammopathy as the underlying cause of the patient's systemic amyloidosis and consequent nephrotic syndrome. It is recommended that immunostaining of amyloid become a routine procedure to detect occult or apparently inactive disease.