WBR0812

Author	[[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathophysiology
Sub Category	SubCategory::Renal
Prompt	[[Prompt::A 45-year-old man is referred by the primary care physician to the nephrologist's office. The patient is found to have elevated levels of anti-phospholipase A2 receptor (PLA2R) antibodies. The patient then undergoes a kidney biopsy that demonstrates subepithelial deposits and capillary wall thickening with normal cellularity. Anti-PLA2R IgG antibodies and C3 deposits are also observed on immunofluorescence. What is the most likely clinical presentation associated with this patient's condition?]]
Answer A	AnswerA::Cola-colored urine and high blood pressure
Answer A Explanation	[[AnswerAExp::Hematuria and hypertension are signs of nephritic syndrome, which are common findings among patients with glomerulonephritis such as IgA nephropathy and rapidly progressive glomerulonephritis. In children, post-infectious glomerulonephritis and Alport syndrome are common etiologies of nephritic syndrome.]]
Answer B	AnswerB::Peripheral edema and frothy urine
Answer B Explanation	[[AnswerBExp::Membranous nephropathy is characterized by the presence of antibodies against phospholipase A2 receptor (PLA2R). Most commonly, patients present with nephrotic syndrome, which is characterized by hypoalbuminemia, peripheral edema, dyslipidemia, and albuminuria (frothy urine).]]
Answer C	AnswerC::Urination that awakens the patient at night
Answer C Explanation	AnswerCExp::Patients with membranous nephropathy do not classically have nocturia. Nocturia may be the first sign of renal insufficiency.
Answer D	AnswerD::Burning sensation upon urination
Answer D Explanation	AnswerDExp::Dysuria is a symptom of urinary tract infection.
Answer E	AnswerE::Malar rash, pallor, and photosensitivity
Answer E Explanation	AnswerEExp::These are the classical findings of systemic lupus erythematosus (SLE). Patients with SLE may progress with renal involvement (commonly lupus nephritis). Lupus nephritis has a wide range of presentations and several sub-types.
Right Answer	RightAnswer::B
Explanation	[[Explanation::Membranous nephropathy (MN) or membranous glomerulonephritis (MGN) is a common glomerulonephritis that usually presents with nephrotic-range proteinuria, edema, and hypertension. MN is generally classified as primary (idiopathic) or secondary to other systemic disease, such as infections, malignancies, or vasculitides. Primary MN has been associated with the presence of a newly discovered phospholipase A2 receptor (PLA2R) nephrotigenic antigen on the membrane surface of glomerular podocytes and anti-PLA2R antibodies. Kidney biopsy remains the gold standard for the diagnosis of MN, which demonstrates subepithelial deposits with capillary wall thickening and IgG deposition under immunofluorescence. On electron microscopy, MN shows a "spike and dome" appearance with subepithelial deposits. While MN is widely considered a chronic condition with a waxing and waning course, it is usually self-limited in the majority of cases. Heavy proteinuria, a significant marker of prognosis, indicates the need for intervention, usually with corticosteroids and immunosuppressive therapy. Educational Objective: Anti-phospholipase A2 receptor antibodies are nephritogenic antibodies associated with membranous nephropathy. They are classically present in sera of patients with membranous nephropathy and as IgG deposits on podocyte surfaces. References: Beck LH Jr, Bonegio RG, Lambeau G, et al. M-type phospholipase A2 receptor as target antigen in idiopathic membranous nephropathy. N Engl J Med. 2009;361(1):11-21. Qin W, Laurence H, Beck LH Jr, Zeng C, et al. Anti-phospholipase A2 receptor antibody in membranous nephropathy. J Am Soc Nephrol. 2011;22:1137-1143. First Aid 2014 page]]
Approved	Approved::Yes
Keyword	WBRKeyword::Membranous nephropathy, WBRKeyword::PLA2R, WBRKeyword::Phospholipase A2 receptor, WBRKeyword::Kidney biopsy, WBRKeyword::Renal biopsy
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