Physiological Adaptation Q 65
Which of the following conditions most commonly causes acute glomerulonephritis?
A. A congenital condition leading to renal dysfunction.
B. Prior infection with group A Streptococcus within the past 10-14 days.
C. Viral infection of the glomeruli.
D. Nephrotic syndrome.
Correct Answer: B. Prior infection with group A Streptococcus within the past 10-14 days.
Acute glomerulonephritis is most commonly caused by the immune response to a prior upper respiratory infection with group A Streptococcus. PSGN most commonly presents in children 1 to 2 weeks after a streptococcal throat infection, or within 6 weeks following a streptococcal skin infection. Group A Streptococcus (GAS) has been subtyped depending on the surface M protein and opacity factor, which are known to be nephrogenic and can cause PSGN.
Option A: Glomerulonephritis is not a congenital condition. Nephrogenic streptococci infection precedes PSGN, which initially affects skin or oropharynx. More recently, PSGN is associated with skin infections (impetigo) more frequently than throat infections (pharyngitis).
Option C: Glomerular lesions in acute GN are the result of glomerular deposition or in situ formation of immune complexes. Poor hygiene, overcrowding, and low socioeconomic status are important risk factors for streptococci outbreaks, and this explains the higher incidence of PSGN in impoverished countries. Genetic factors are expected to predispose to the condition since almost 40% of patients with PSGN gave a positive family history. There is no specific gene found to cause PSGN.
Option D: Nephrotic syndrome is the combination of nephrotic-range proteinuria with a low serum albumin level and edema. It is caused by increased permeability through the damaged basement membrane in the renal glomerulus, especially infectious or thrombo-embolic. It is the result of an abnormality of glomerular permeability that may be primary with a disease-specific to the kidneys or secondary to congenital infections, diabetes, systemic lupus erythematosus, neoplasia, or certain drug use.