Glomerular and Vascular Disorders
Core concepts
Nephrotic syndrome is defined by heavy proteinuria, hypoalbuminemia, edema, and hyperlipidemia; in children, minimal change disease is the most common cause and is usually steroid-sensitive. Nephritic syndrome is defined by hematuria with red-cell casts, hypertension, oliguria, and azotemia. Differentiate the two first, because management and biopsy thresholds differ.
Key entities include post-infectious glomerulonephritis (low C3, cola-colored urine, hypertension, streptococcal evidence), IgA nephropathy and IgA vasculitis (synpharyngitic hematuria, normal complement), membranoproliferative GN (persistently low C3), lupus nephritis (multisystem, low C3/C4, anti-dsDNA), Alport syndrome (hematuria, sensorineural hearing loss, ocular findings, family history), thin basement membrane nephropathy, and hemolytic uremic syndrome (microangiopathic anemia, thrombocytopenia, AKI; Shiga toxin-associated versus complement-mediated atypical HUS). FSGS causes steroid-resistant nephrotic syndrome and may recur after transplant.
Traps
Do not label every nephrotic child as minimal change disease without checking for atypical features: age under 1 year, hypertension, hematuria, low complement, or steroid resistance should prompt biopsy. Steroid resistance is failure to remit after 4-6 weeks of adequate prednisone, not a single day of poor response. Complement levels help: low C3 with nephritis suggests post-infectious GN, MPGN, or lupus; normal complement suggests IgA nephropathy or thin basement membrane disease. In Shiga toxin-associated HUS, antibiotics and antimotility agents are generally avoided.
Worked example / rule of thumb
A 6-year-old with periorbital edema, albumin 1.5 g/dL, urine protein 4+, no hematuria, normal complement, and normal blood pressure most likely has minimal change disease. Start prednisone 60 mg/m2/day (maximum 60 mg) for 4-6 weeks, then taper. Rule: nephrotic = proteinuria plus hypoalbuminemia and edema; nephritic = hematuria plus hypertension and azotemia.