WBR0388

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 7-year-old boy is brought by his mother to his pediatrician for red-colored urine and oliguria. The patient does not have any chronic condition and does not take any medication. Upon further questioning, the mother explains that her son has recovered from a streptococcal pharyngitis 10 days prior to presentation. Physical examination is remarkable for periorbital and peripheral edema. The patient undergoes further work-up, and serum activities of complements C3 and C5 and properdin (Factor P) are measured. Which of the following set of activities of C3, C5, and properdin is most likely associated with this patient's condition? ]]
Answer A	AnswerA::A
Answer A Explanation	AnswerAExp::Following activation of the alternative complement pathway, serum concentrations of complements is reduced, not elevated.
Answer B	AnswerB::B
Answer B Explanation	AnswerBExp::C3 is generally reduced to a greater extent than C5 in the case of APSGN.
Answer C	AnswerC::C
Answer C Explanation	AnswerCExp::C5 and properdin would not be elevated in APSGN.
Answer D	AnswerD::D
Answer D Explanation	AnswerDExp::Serum concentrations of the alternative pathway complements C3 and C5 and properdin will be reduced in APSGN.
Answer E	AnswerE::E
Answer E Explanation	AnswerEExp::Properdin is a component of the alternative pathway. Similar to C3 and C5, its serum concentration also decreases in APSGN.
Right Answer	RightAnswer::D
Explanation	[[Explanation::Acute post-streptococcal glomerulonephritis (APSGN) is the most common cause of nephritic syndrome (hematuria, hypertension, azotemia, oliguria, and edema) in the pediatric population. It is characterized by glomerular enlargement and proliferation of cellular components on light microscopy and a starry sky granular appearance (lumpy-bumpy) with antibody and complement deposition along the mesangium and the glomerular basement membrane on immunofluorescence. It occurs secondary to immunologic reaction that occurs 1 to 2 weeks following a nephritogenic group A streptococcal infection (pharyngitis or impetigo). The majority of cases of APSGN are self-limited, and complete resolution often occurs 1 to 2 months following initiation of symptoms. APSGN is characterized by hypocomplementemia with reduced serum C3, C5, and properdin (Factor P) due to alternative pathway activation. Properdin, a gamma globulin protein, is a positive regulator that stabilizes convertase, whose activity is required for the activation of the alternative pathway. Normalization of complement concentration, and increase in concentrations in some cases, can be delayed and occur 2-12 weeks following the onset of symptoms. Educational Objective: Acute post-streptococcal glomerulonephritis (APSGN) is a type of acute nephritic syndrome that occurs secondary to a group A streptococcal pharyngitis or impetigo. Serum concentrations of alternative pathway complements C3 and C5 and properdin will be reduced in APSGN. References: Wyatt RJ, Forristal J, Clark DW, Sugimoto S, et al. Complement profiles in acute post-streptococcal glomerulonephritis. Pediat Nephrol. 1988;2:219-223. First Aid 2014 page 538]]
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