WBR0388

{{WBRQuestion |QuestionAuthor=Rim Halaby, M.D. [1] |ExamType=USMLE Step 1 |MainCategory=Pathology |SubCategory=Renal |MainCategory=Pathology |SubCategory=Renal |MainCategory=Pathology |SubCategory=Renal |MainCategory=Pathology |MainCategory=Pathology |SubCategory=Renal |MainCategory=Pathology |SubCategory=Renal |MainCategory=Pathology |SubCategory=Renal |MainCategory=Pathology |SubCategory=Renal |MainCategory=Pathology |MainCategory=Pathology |SubCategory=Renal |Prompt=A 7 year old male patient is brought by his mother to his pediatrician for red-colored urine. 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 two weeks prior to presentation. Physical examination is completely unremarkable. Work-up for the patient’s urinary condition includes serum activity of complements C3 and C5, and properdin (Factor P). Blood is immediately withdrawn. Which of the following set of activities is most likely to be present in this patient for C3, C5, and Properdin (in order)?

[[Image: |Explanation=Acute post-streptococcal glomerulonephritis (APSGN) is a type of acute nephritic syndrome associated with glomerular enlargement and proliferation of cellular components. It occurs secondary to immunologic reaction following nephritogenic group A streptococcal infection, usually pharyngitis or impetigo.

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. To note, normalization of complement concentration, and increase in concentrations in some cases, can occur anytime within 2-12 weeks of onset.

Educational Objective: Acute post-streptococcal glomerulonephritis 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.

Reference: Wyatt RJ, Forristal J, Clark DW, Sugimoto S, et al. Complement profiles in acute post-streptococcal glomerulonephritis. Pediat Nephrol. 1988;2:219-223.

|AnswerA=Increased - Increased - Increased |AnswerAExp=Following activation of alternative complement pathway, serum concentrations of complements is reduced, not elevated. |AnswerB=Increased - Decreased - Decreased |AnswerBExp=C3 is generally reduced to a greater extent than C5 in the case of APSGN. |AnswerC=Decreased - Increased - Increased |AnswerCExp=C5 and Properdin would not be elevated in APSGN. |AnswerD=Decreased - Decreased - Decreased |AnswerDExp=Serum concentrations of alternative pathway complements C3 and C5, and properdin will be reduced in APSGN. |AnswerE=Decreased - Decreased - Increased |AnswerEExp=Properdin is a component of the alternative pathway. Similar to C3 and C5, its serum concentration also decreases in APSGN. |Approved=No }}