Nephritic/Nephrotic? Flashcards
Post-strep glomerulonephritis presents with? Latency period?
This patient is presenting with worsening hematuria, swelling, malaise, and elevated creatinine 3 weeks after tonsillitis which was treated with amoxicillin. The urinalysis is notable for red blood cell casts and hematuria which are concerning for some kind of nephritic syndrome and the renal biopsy is consistent with an immunoglobulin-related process.
Post-streptococcal glomerulonephritis (PSGN), specifically, is the most common cause of acute nephritis in children in the world. PSGN is caused by glomerular immune complex deposition resulting on complement activation. A classic clinical history includes a recent group A streptococcal (GAS) skin or pharyngeal infection. The latent period between infection and nephritis is 1-3 weeks following pharyngitis and 3-6 weeks following skin infection. Symptoms are those of nephritis in general, with hematuria, proteinuria, pyuria, hypertension, edema, and renal dysfunction. Complement is almost always low. Streptococcal antibody titers can be checked, but are rarely needed for diagnosis. Treatment is supportive, but in severe cases, steroids can be considered. Some patients will go on to require dialysis, but most patients do eventually make a full renal recovery, especially children.
Renal Biopsy findings of Post-strep glomerulonephritis?
renal biopsy that demonstrates bumpy deposits of immunoglobulin G on the renal basement membrane, but can be complement or IgM deposition as well.
Which types of strep infections can cause post-infectious glomerulonephritis? How do we diagnose? If in doubt can do what? how does this test work?
Cellulitis and pharyngitis are often caused by streptococcal species and both are known to cause post-infectious glomerulonephritis. This patient’s urinalysis with active urine sediment (WBCs, RBCs, and protein), depressed C3 (due to immune complex deposition), and elevated creatinine are concerning for glomerulonephritis. Most of the time, post-streptococcal (a form of post-infectious) glomerulonephritis is diagnosed clinically, but if there is uncertainty about whether or not a recent infection was due to streptococcus, a streptozyme test can be obtained. It will be positive about 95% of the time after pharyngeal streptococcal infections and about 80% of the time after skin and soft tissue infections.
A streptozyme test measures antibodies against 5 different streptococcal antigens (including anti-streptolysin [ASO]) rather than just a single antigen as was often done prior. The antibodies tested are noted below and can still be tested individually if desired. The reason this test was created is that ASO titers alone are often falsely low or negative in patients with streptococcal skin infection, such as this one.
If there is a history of recent streptococcal infection, the diagnosis is usually made without a renal biopsy. If there is a concern for an alternative diagnosis, a biopsy may be pursued
IgA nephropathy? Main difference with post infectious?
This patient is presenting with a recent upper respiratory tract infection associated with the development of gross hematuria, which is now microscopic hematuria. He has no elevation in creatinine or electrolytes. The development of gross hematuria after an upper respiratory tract infection is commonly associated with IgA nephropathy. About 50% of patients will present with recurring episodes of gross hematuria after upper respiratory tract infections. Another 40% often have microscopic hematuria or mild proteinuria detected on routine evaluation as they never notice hematuria. Less than 10% of patients will develop an acute nephrotic syndrome progressing to significant glomerulonephritis.
IgA nephropathy is highly associated with upper respiratory or gastrointestinal infections and is classically seen in young males. Episodic frank hematuria occurs in nearly 50% of all cases and usually starts within a day of an upper respiratory tract infection (as opposed to poststreptococcal glomerulonephritis, which typically occurs around 1 to 3 weeks after infection with group A beta-hemolytic Streptococcus). The frank hematuria often resolves after a few days; however, the microscopic hematuria may continue to persist. IgA nephropathy occurs due to deposition of the IgA antibody in the glomerulus. Henoch-Schönlein purpura is highly associated with IgA nephropathy and is thought to be a systemic form of the disease. Henoch-Schönlein purpura presents with “palpable purpura” and is commonly seen in young adults aged 16 to 35.
Postinfectious glomerulonephritis is typically seen within 1 to 3 weeks of a group A beta-hemolytic streptococcal infection and presents with oliguria, edema, hypertension, and smokey-brown urine. Look for low serum C3, an increased ASO titer, and lumpy-bumpy immunofluorescence. Treatment involves supportive measures only as most patients will have complete recovery. This patient had hematuria in close proximity to his upper respiratory infection, making postinfectious glomerulonephritis much less likely.
Alport syndrome?
Hereditary nephritis is also known by the eponym Alport syndrome and is similar to the disease “thin basement membrane nephropathy” (TBMN). Importantly, the medical community and consequently test writers are removing eponyms associated with diseases and syndromes. Unfortunately, it has become important to know both eponyms and proper names. The classic triad of nephritic syndrome, sensorineural hearing loss, and ocular abnormalities of the lens, retina, or cornea characterize this disease spectrum. Additional associations include leiomyomas and arterial aneurysms. As the disease is most often inherited in an X-linked pattern, males are more commonly affected. The mutation associated with X-linked disease is in type 4 collagen, specifically COL4A5. This patient presents with nephritic syndrome as evidenced by his edema, elevated blood pressure, hematuria, and proteinuria. The addition of hearing difficulties in this young male should raise concern for hereditary nephritis or Alport syndrome.
The American Society of Nephrology has subtle distinctions between hereditary nephritis and TBMN, and is included here for the sake of completeness. While hereditary nephritis and Alport syndrome are synonymous, the term “thin basement membrane nephropathy” is reserved for individuals with isolated glomerular hematuria with a thinned GBM, due to mutations in COL4A3 or COL4A4, but not COL4A5.
