A renal biopsy from a patient with long-standing rheumatoid arthritis reveals amorphous, eosinophilic deposits in the glomeruli that stain positive with Congo red and show apple-green birefringence under polarized light. What is the most likely diagnosis?

The correct answer to the question "A renal biopsy from a patient with long-standing rheumatoid arthritis reveals amorphous, eosinophilic deposits in the glomeruli that stain positive with Congo red and show apple-green birefringence under polarized light. What is the most likely diagnosis?" is Option B: Amyloidosis.

The other options — A) Diabetic nephropathy, C) Minimal change disease, D) Focal segmental glomerulosclerosis — are incorrect for this USMLE Exam Prep question. As explained above: The description of amorphous, eosinophilic deposits that stain positive with Congo red and exhibit apple-green birefringence under polarized light is pathognomonic for amyloidosis. This condition oft…