WBR230
| Author | [[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Will Gibson)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Pathology |
| Sub Category | SubCategory::Renal |
| Prompt | [[Prompt::A 21-year-old man presents to the urgent care clinic for dark colored urine. Upon further questioning, the patient reports he has recently recovered from a flu-like illness 4 days prior to presentation. Patient denies dysuria, frequency, or urgency. Patient’s vital signs reveal a temperature of 36.7 degree C (98 degree F), heart rate of 68 beats per minute, and blood pressure measuring 110/85 mmHg. Patient’s physical examination is unremarkable. After appropriate work-up, renal biopsy reveals mesangial proliferation. Which finding is most consistent with the pathogenesis of the patient’s condition?]] |
| Answer A | AnswerA::Deposition of an immunoglobulin subclass deficient in galactose |
| Answer A Explanation | [[AnswerAExp::IgA nephropathy (Berger’s disease) is the most common primary glomerulonephritis worldwide. It is characterized by deposition of IgA in the glomerular mesangium leading to mesangial proliferation. The IgA1 is almost always the subclass involved and contains O-glycans deficient in galactose.]] |
| Answer B | AnswerB::Circulating immune complexes triggering the activation of complement pathways |
| Answer B Explanation | [[AnswerBExp::Circulating immune complexes that trigger the activation of complement pathways are typically seen in post-infectious glomerulonephritis and in membranoproliferative glomerulonephritis.]] |
| Answer C | AnswerC::Selective loss of albumin caused by basement membrane polyanion loss |
| Answer C Explanation | [[AnswerCExp::Selective loss of albumin is a hallmark of minimal change disease (lipoid nephrosis). Characteristically, light microscopy in minimal change disease reveals normal glomeruli. Electron microscopy shows podocyte foot process effacement.]] |
| Answer D | AnswerD::Deposition of protein sheets that stain positive for Congo Red |
| Answer D Explanation | [[AnswerDExp::Amyloidosis is an infiltrative disease that has a positive Congo red stain showing apple-green birefringence.]] |
| Answer E | AnswerE::Generation of advanced glycosylation end products and acceleration of aldose reductase pathway |
| Answer E Explanation | [[AnswerEExp::Advanced glycosylation end products (AGEs) are the hallmark of diabetic nephropathy causing microvascular complications.]] |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::IgA nephropathy (Berger’s disease) is the most common primary glomerulonephritis worldwide. It is characterized by deposition of IgA and C3 in the glomerular mesangium leading to mesangial proliferation that can be observed on light microscopy. While IgG and/or IgM could also be found, IgA is the predominant antibody subtype detected and is almost always the IgA1 subclass that contains O-glycans deficient in galactose. Complement C3, properdin, C4, C4d, mannose-binding lactin, and terminal complement complex C5b-C9 are also commonly present; while C1q is typically absent. On light microscopy, increase in mesangial matrix and hypercellularity are common but not exclusive. Electron microscopy reveals electron-dense material corresponding to granular IgA immune deposits mostly seen in mesangial and paramesangial areas.
As opposed to post-infectious glomerulonephritis, IgA nephropathy is typically “synpharyngitic” due to its manifestation immediately following a non-specific upper respiratory tract or gastrointestinal infection.The peak incidence of IgA Nephropathy is between the ages of 15 and 30, and males are affected twice as often as females. Genome-wide-association studies have linked the HLA and complement loci to disease predisposition. No curative treatment is available for IgA nephropathy, and optimal management consists of blood pressure control with an ACE-inhibitor or Angiotensin Receptor Blocker (ARB). Although kidney transplantation may be curative for some patients, recurrence rates are high ranging from 30 to 60%. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Renal, WBRKeyword::Nephropathy, WBRKeyword::IgA Nephropathy, WBRKeyword::Autoimmune, WBRKeyword::IgA, WBRKeyword::Kidney, WBRKeyword::Nephritis, WBRKeyword::Nephritic syndrome, WBRKeyword::Berger disease, WBRKeyword::Hematuria, WBRKeyword::Histology |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |