WBR0292

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Author [[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Pathology
Sub Category SubCategory::Renal
Prompt [[Prompt::A 68-year-old man presents to his physician for his annual check-up. The patient’s past medical history is significant for hypertension well-controlled on lisinopril and advanced type II diabetes mellitus poorly controlled on daily insulin injections. Routine work-up reveals elevated serum creatinine. A renal biopsy under light microscopy similar to the patient’s biopsy is shown in the image below. The following findings could be best explained by which of the following pathologic processes?

]]

Answer A AnswerA::Amorphous pink deposits of amyloid in renal cortex
Answer A Explanation [[AnswerAExp::Amyloidosis is characterized by amyloid deposition that is positive for Congo red stain.]]
Answer B AnswerB::Immune response mediated by CD4 and CD8 lymphocytes
Answer B Explanation [[AnswerBExp::Immune response mediated by CD4 and CD8 lymphocytes describes the mechanism of renal rejection following transplantation.]]
Answer C AnswerC::Cystic distribution throughout the renal parenchyma
Answer C Explanation [[AnswerCExp::Polycystic kidney disease is characterized by cystic distribution throughout the renal parenchyma.]]
Answer D AnswerD::Immune complex deposition activating the complement pathway
Answer D Explanation [[AnswerDExp::The pathogenesis of several primary glomerulonephritides, including post-infectious glomerulonephritis and membranoproliferative glomerulonephritis, is characterized by immune complex deposition that activates the complement pathway.]]
Answer E AnswerE::Non-enzymatic glycosylation of proteins
Answer E Explanation AnswerEExp::Diabetic nephropathy is a common microvascular complication in advanced diabetes mellitus. Renal biopsy under light microscopy would reveal characteristic eosinophilic nodules in the glomerular tuft called “Kimmelsteil-Wilson” lesion.
Right Answer RightAnswer::E
Explanation [[Explanation::Diabetic nephropathy is a common microvascular complication of advanced diabetes mellitus. Renal biopsy under light microscopy typically demonstrates characteristic eosinophilic nodules in the glomerular tuft called “Kimmelsteil-Wilson” lesions. Chronic hyperglycemia results in accumulation of advanced glycosylation end-products (AGEs) that trap extravasated immunoglobulins, albumin, LDL, and other proteins via cross-linking to the extravascular matrix.

Educational Objective: Diabetic nephropathy is a microvascular complication of uncontrolled diabetes mellitus. It is characterized by Kimmelsteil-Wilson lesions, which are eosinophilic nodules in glomerular tufts. The pathogenesis of diabetic nephropathy is thought to be due to accumulation of advanced glycosylation end-products (AGEs).
References: Kalia K, Sharma S, Mistry K. Non-enzymatic glycosylation of immunoglobulins in diabetic nephropathy. Clin Chim Acta. 2004;347(1-2):169-76. First Aid 2014 page 327, 537]]

Approved Approved::Yes
Keyword WBRKeyword::Diabetic nephropathy, WBRKeyword::Diabetes mellitus, WBRKeyword::Kimmelsteil-Wilson lesion, WBRKeyword::Microvascular complication, WBRKeyword::Renal failure, WBRKeyword::Glomerulonephritis
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