glomerulonephritides

Glomerulonephritides (GN) encompass a diverse group of renal diseases involving inflammation and damage to the glomerular capillaries, the filtering units of the kidney. They are typically categorized into two main clinical syndromes: nephritic syndrome and nephrotic syndrome, though overlap can occur.

Nephritic syndrome is characterized by hematuria (often with dysmorphic RBCs and RBC casts), mild-to-moderate proteinuria, hypertension, and oliguria due to decreased GFR. Classic causes include: - Post-streptococcal GN (immune complex deposition following Group A Strep infection, subepithelial 'humps' on EM, granular IF pattern) - IgA nephropathy (Berger disease) - most common GN worldwide, mesangial IgA deposits, often follows mucosal infections - Rapidly progressive GN (RPGN) - crescentic GN, associated with anti-GBM disease (Goodpasture syndrome), ANCA-associated vasculitis (granulomatosis with polyangiitis, microscopic polyangiitis), or immune complex disease - Lupus nephritis (various classes, subendothelial deposits, 'wire-loop' lesions) - Alport syndrome (hereditary, type IV collagen defect, associated with sensorineural hearing loss and ocular abnormalities)

Nephrotic syndrome is characterized by massive proteinuria (>3.5g/day), hypoalbuminemia, edema, hyperlipidemia, and lipiduria. Classic causes include: - Minimal change disease (most common in children, effacement of foot processes on EM, responsive to steroids) - Focal segmental glomerulosclerosis (FSGS) - common in adults, associated with HIV, heroin use, obesity - Membranous nephropathy - subepithelial deposits, 'spike and dome' pattern, associated with malignancy, hepatitis B, and PLA2R antibodies - Membranoproliferative GN (MPGN) - 'tram-track' appearance, associated with hepatitis C - Diabetic nephropathy - Kimmelstiel-Wilson nodules - Amyloidosis - Congo red staining with apple-green birefringence

Diagnosis relies on urinalysis, serum complement levels (C3/C4), autoantibody testing (ANA, ANCA, anti-GBM), and renal biopsy with light microscopy, immunofluorescence, and electron microscopy to characterize the specific pattern of injury. Treatment varies by etiology but may include immunosuppression (corticosteroids, cyclophosphamide, rituximab), ACE inhibitors/ARBs for proteinuria reduction, and management of underlying systemic disease. Prognosis ranges from self-limited (post-strep GN in children) to progressive renal failure requiring dialysis or transplant (RPGN, FSGS).