Kidney-limited AL amyloidosis: a case report and review of the literature

Amyloidosis involves the deposition of abnormal proteins in various tissues and results in progressive organ dysfunction, commonly affecting multiple organs. Two types of systemic amyloidosis are AA and AL; the former is associated with acute phase reactions and the latter is composed of light chain immunoglobulins. This disease commonly affects the kidneys and is evidenced by massive proteinuria. A biopsy is the gold standard of diagnosis, with Congo Red staining revealing an apple-green birefringence under polarized light. Although the kidneys are frequently affected in this disease, it is rare that amyloidosis is limited to the kidneys without involvement of other organs. We present an 83-year-old female with bilateral lower extremity swelling for several months who was found to have 12.374 grams of protein in a 24-hour urine sample and a large amount of free lambda chains. A renal biopsy demonstrated renal amyloidosis of the AL type. Serum immunofixation and flow cytometry were unremarkable for any plasma dyscrasia; a bone marrow biopsy did not reveal systemic amyloidosis and imaging with PET/CT scan did not show evidence of other organ involvement. She was diagnosed with renal-limited amyloidosis and started on bortezomib, melphalan, and steroids. Clinicians should be aware of the signs and symptoms of amyloidosis, specifically its ability to present with unusual involvement of individual organs.