Renal · Glomerular Diseases
The facts most likely to be tested
Post-streptococcal glomerulonephritis presents 1–3 weeks after a group A beta-hemolytic streptococcal pharyngitis or skin infection with cola-colored urine and low C3 complement levels.
IgA nephropathy (Berger disease) is the most common cause of glomerulonephritis and typically presents as recurrent gross hematuria occurring concurrently with an upper respiratory tract infection.
Goodpasture syndrome (anti-GBM disease) involves linear IgG deposits on immunofluorescence and presents with the classic triad of hemoptysis, hematuria, and renal failure.
Rapidly progressive glomerulonephritis (RPGN) is characterized by the formation of crescents on light microscopy, representing a medical emergency requiring urgent renal biopsy and corticosteroids.
Alport syndrome is an X-linked defect in type IV collagen that manifests as the triad of sensorineural hearing loss, ocular abnormalities (e.g., anterior lenticonus), and hematuria.
Membranoproliferative glomerulonephritis (MPGN) is associated with hepatitis C infection and presents with a tram-track appearance on light microscopy due to subendothelial immune complex deposition.
Nephritic syndrome is clinically defined by the presence of dysmorphic red blood cells, red cell casts, hypertension, and azotemia.
Vignette unlocked
A 28-year-old male presents to the emergency department with a 2-day history of hemoptysis and dark-colored urine. He reports a recent viral illness 1 week ago. Physical examination reveals bilateral crackles on lung auscultation and elevated blood pressure of 155/95 mmHg. Laboratory studies show an elevated serum creatinine and urinalysis demonstrates dysmorphic red blood cells and red cell casts. A renal biopsy is performed, revealing linear IgG deposits along the glomerular basement membrane.
What is the most likely diagnosis?
Goodpasture syndrome (anti-GBM disease)
The vignette tests the classic presentation of Goodpasture syndrome, characterized by pulmonary-renal syndrome and the pathognomonic finding of linear IgG deposits on immunofluorescence.
Full handout
High yield triage
Etiology / Epidemiology
Post-infectious (Group A Strep) is most common in children; IgA nephropathy is the most common primary glomerulonephritis in adults.
Clinical Manifestations
Classic nephritic syndrome triad: hematuria (cola-colored urine), hypertension, and edema.
Diagnosis
Renal biopsy is the gold standard for definitive diagnosis; urinalysis shows dysmorphic RBCs and RBC casts.
Treatment
ACE inhibitors are first-line for proteinuria/HTN; corticosteroids or immunosuppressants for severe/crescentic disease.
Prognosis
Rapidly progressive glomerulonephritis (RPGN) leads to end-stage renal disease within weeks to months if untreated.
Full handout
Epidemiology & Etiology
Post-streptococcal glomerulonephritis (PSGN) typically follows pharyngitis or impetigo by 1-3 weeks. IgA nephropathy often presents after a mucosal infection (synpharyngitic). Systemic diseases like Lupus nephritis and Goodpasture syndrome are critical secondary causes.
Pertinent Anatomy
The glomerulus is the primary site of injury, specifically the capillary basement membrane and mesangium. Damage disrupts the filtration barrier, allowing leakage of blood and protein into the urinary space.
Pathophysiology
Immune complex deposition triggers an inflammatory cascade involving complement activation and neutrophil infiltration. This leads to proliferative changes, reduced glomerular filtration rate (GFR), and subsequent sodium/water retention. Severe injury causes crescent formation, a hallmark of rapidly progressive disease.
Clinical Manifestations
Patients present with cola-colored urine (hematuria) and oliguria. Physical exam reveals periorbital edema and hypertension. Pulmonary hemorrhage is a red flag for Goodpasture syndrome (anti-GBM disease).
Diagnosis
Urinalysis reveals RBC casts and dysmorphic RBCs, which are pathognomonic for glomerular bleeding. Renal biopsy is the gold standard to determine the specific histologic subtype. Serum complement levels (C3/C4) are often low in PSGN and lupus nephritis.
Treatment
Management focuses on blood pressure control using ACE inhibitors or ARBs to reduce intraglomerular pressure. Corticosteroids and cyclophosphamide are reserved for aggressive, crescentic forms. Diuretics are used for volume overload, but potassium-sparing agents should be avoided in renal insufficiency.
Prognosis
Prognosis depends on the underlying histology; crescentic patterns carry a poor prognosis without aggressive intervention. Patients require long-term monitoring of serum creatinine and proteinuria to assess for progression to chronic kidney disease.
Differential Diagnosis
Nephrotic syndrome: massive proteinuria (>3.5g/day) and hypoalbuminemia
IgA nephropathy: synpharyngitic hematuria
Post-streptococcal: low C3 levels and recent skin/throat infection
Goodpasture syndrome: hemoptysis and anti-GBM antibodies
Alport syndrome: sensorineural hearing loss and family history