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Case History

A 76-year-old male with acute renal insufficiency and a recent diagnosis of multiple myeloma presents with hematuria, urine protein 15g/24 hours, creatinine 4.96, and a positive M spike. Which stain would you order next?

  1. Oil red O
  2. GMS
  3. Congo Red
  4. Colloidal Iron

EMpic HandEpic Kappapic Lambdapic

Answer: ā€œCā€. Congo Red

Diagnosis: Immunoglobulin light chain (AL) amyloidosis

Amyloid usually appears as an amorphous, pink, waxy infiltrate in glomeruli and blood vessels on light microscopy. The presence of amyloid fibrils are confirmed by electron microscopy. The fibrils are composed of fragments of monoclonal light chains, most commonly lambda. They have a characteristic ability to bind Congo red, leading to green birefringence under polarized light.

Patients may develop amyloidosis either alone or in association with plasma cell dyscrasias, such as multiple myeloma. AL amyloidosis is a clonal plasma cell disorder and is treated with chemotherapy to eradicate the problematic clone. Approximately 70% of patients develop and present with renal involvement.   

Case contributed by Lindsay Matthews, M.D., Surgical Pathology Fellow, UAB Department of Pathology