WBR0647

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pathology, MainCategory::Pathophysiology
Sub Category	SubCategory::Renal
Prompt	[[Prompt::A 4 year old boy is brought to the emergency department by his mother for facial edema that started gradually 2 days ago. The mother reports that her son was complaining of fatigue for the past week which she attributed to his lack of sleep. She also explains that he suffered from a sore throat 2 weeks ago which was thought to be viral and for which he did not receive any antibiotics. On physical exam you notice marked facial edema with no obvious erythema or rash. You also note that the child's legs and feet are swollen which the mother confirms is more than their usual plump appearance. You order a urinalysis that shows a few red blood cells with a markedly elevated protein-to-creatinine ratio and an estimated 24 hour urine protein of 3.6 g. Which of the following glomerular structures is the most likely to be involved in this patient? ]]
Answer A	AnswerA::A
Answer A Explanation	AnswerAExp::This refers to the glomerular capillary or endothelial cell. Endothelial involvement is not seen in MCD. It may be seen in lupus nephritis or membranoproliferative glomerulonephritis.
Answer B	AnswerB::B
Answer B Explanation	AnswerBExp::Mesangial involvement is seen in IgA nephropathy usually not in MCD.
Answer C	AnswerC::C
Answer C Explanation	AnswerCExp::This refers to the podocyte. Although the foot processes of the podocyte are effaced, the cell itself is not affected.
Answer D	AnswerD::D
Answer D Explanation	AnswerDExp::This refers to the glomerular basement membrane which is usually spared in MCD. It is involved in the pathogenesis of Alport syndrome and membranoproliferative glomerulonephritis among others.
Answer E	AnswerE::E
Answer E Explanation	AnswerEExp::This refers to the podocyte foot processes which are usually effaced in MCD and are the cause of the proteinuria.
Right Answer	RightAnswer::E
Explanation	[[Explanation:: Minimal change disease (MCD), also known as lipoid nephrosis, is the most common primary nephrotic syndrome in childhood accounting for >85% of all cases. It usually presents in young children often after an upper respiratory infection. Clinically, the hallmark of MCD like most nephrotic syndromes is edema and massive proteinuria > 3 g/24h (classically selective to albumin) with minimal to absent hematuria. MCD is a T-cell mediated glomerular disease whose cause is not well understood. On light microscopy, kidney biopsy is usually normal or shows very mild lipid accumulation in tubular cells (hence the name lipoid nephrosis). Definitive diagnosis usually requires electron microscopy of the biopsy specimen that would show retained podocytes but with effacement of the podocyte foot processes. The treatment of choice is corticosteroids with 90% of patients responding within 2 weeks of initiation. Learning objectives: Minimal change disease is the most common cause of nephrotic syndrome in childhood. It is caused by podocyte foot process effacement. References: Grimbert P, Audard V, Remy P, Lang P, Sahali D. Recent approaches to the pathogenesis of minimal-change nephrotic syndrome. Nephrol Dial Transplant. 2003;18(2):245-8. The primary nephrotic syndrome in children. Identification of patients with minimal change nephrotic syndrome from initial response to prednisone. A report of the International Study of Kidney Disease in Children. J Pediatr. 1981;98(4):561-4. Educational Objective: References: ]]
Approved	Approved::No
Keyword	WBRKeyword::Minimal change disease, WBRKeyword::proteinuria, WBRKeyword::podocyte
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::