{
 "topic": "Nephrotic Syndrome",
 "slug": "nephrotic-syndrome",
 "category_id": 15768,
 "summary": "The nephrotic tetrad, how age and clinical features predict minimal change disease versus other glomerular causes, and the hypercoagulability and infection risks that drive management.",
 "written_by": "claude-sonnet",
 "references": [
  {
   "title": "Update in Pediatrics",
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   "pages": [
    515
   ]
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    596,
    599
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  {
   "title": "Kliegman R. Nelson Textbook of Pediatrics 2-Volume Set 22ed 2024",
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   ]
  },
  {
   "title": "CURRENT Diagnosis and Treatment Pediatrics, Twenty-Fourth Edition",
   "author": "Hay, William W., Levin, Myron J., Deterding, Robin R., Abzug, Mark J.",
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    13
   ]
  },
  {
   "title": "MedStudy Pediatrics Core 11th Edition 2024-2025",
   "author": null,
   "pages": [
    570
   ]
  }
 ],
 "short": [
  {
   "title": "In short",
   "content": "- Nephrotic syndrome = increased glomerular permeability causing heavy proteinuria (>1000 mg/m\u00b2/day, or urine protein:creatinine ratio >2), hypoalbuminemia (serum albumin <3 g/dL), edema, and hyperlipidemia/hypercholesterolemia.\n- Edema develops once fluid overload exceeds about 3\u20135% of body weight, driven by decreased plasma oncotic pressure and renal sodium retention.\n- Minimal change disease (MCD) causes 85\u201390% of primary (idiopathic) pediatric nephrotic syndrome and is the most common form overall, typically presenting in preschool-age children (ages 2\u20136); >80% respond to steroids; microscopic hematuria occurs in about 10\u201320% of cases; complement (C3/C4) levels are normal.\n- Other primary causes \u2014 focal segmental glomerulosclerosis (FSGS) and membranous nephropathy \u2014 are less common than MCD and tend to present in school-age and adolescent children; FSGS is steroid-resistant in 80\u201385% of cases and shows hematuria in 60\u201380%; membranous nephropathy shows hematuria in about 60% and is associated with venous thromboembolism.\n- Membranoproliferative glomerulonephritis (MPGN, also called complement 3 glomerulopathy) shows hematuria in about 80% of cases, hypertension in about 35%, and characteristically low C3.\n- Secondary nephrotic syndrome should be suspected in children over age 12, or with sustained hypertension, hematuria, renal dysfunction, extrarenal symptoms (rash, arthralgias, fever), or depressed complement \u2014 causes include infections (HIV, hepatitis B/C, syphilis, malaria, toxoplasmosis, varicella zoster, and reported cases with acute COVID-19), drugs (NSAIDs, penicillamine, lithium, heavy metals, pamidronate, interferon-gamma), lymphoma/leukemia, SLE, IgA nephropathy, IgA vasculitis (Henoch-Sch\u00f6nlein purpura), postinfectious GN, and MPGN. Malaria and schistosomiasis are leading causes in some world regions.\n- Congenital nephrotic syndrome presents within the first 3 months of life (infantile nephrotic syndrome: 3\u201312 months); most have a genetic basis, though intrauterine infections (congenital syphilis, toxoplasmosis, CMV, HIV) are also implicated.\n- Nephrotic syndrome is a hypercoagulable state from vascular stasis (hemoconcentration, volume depletion), increased platelet number/aggregability, elevated hepatic fibrinogen production, and urinary loss of antithrombotic factors (antithrombin III, protein S); thrombosis can occur in any venous bed including cerebral venous sinus, renal vein, and pulmonary veins \u2014 clinical risk is lower in children (2\u20135%) than adults but can be serious.\n- Urinary immunoglobulin loss increases susceptibility to serious infection (peritonitis, pneumonia, sepsis) from encapsulated organisms, especially Streptococcus pneumoniae and group B streptococcus \u2014 despite overall fluid overload, patients may be intravascularly volume-depleted, an important and counterintuitive clinical trap."
  }
 ],
 "long": [
  {
   "title": "Definition",
   "content": "Nephrotic syndrome is the clinical consequence of increased glomerular permeability, primarily from podocyte injury/dysfunction, resulting in heavy proteinuria \u2014 conventionally defined as urinary protein excretion exceeding 1000 mg/m\u00b2/day, or a random urine protein-to-creatinine ratio greater than 2. This drives the classic tetrad: hypoalbuminemia (serum albumin under 3 g/dL), edema, and hyperlipidemia/hypercholesterolemia, in addition to the proteinuria itself. Edema develops once fluid overload exceeds roughly 3\u20135% of body weight, resulting from a combination of decreased plasma oncotic pressure and renal sodium retention. Nephrotic syndrome can be classified as primary (idiopathic, without evidence of systemic illness), secondary (associated with a systemic disorder), or congenital/infantile based on age of onset and underlying cause."
  },
  {
   "title": "Etiology",
   "content": "Primary nephrotic syndrome accounts for the large majority of pediatric cases, with minimal change disease responsible for 85\u201390% of these; focal segmental glomerulosclerosis (FSGS) and membranous nephropathy are less common primary causes and tend to present in older, school-age and adolescent children rather than preschoolers. Secondary nephrotic syndrome arises from systemic disease and should be specifically suspected in children older than 12 years, or those with sustained hypertension, hematuria, renal dysfunction, extrarenal symptoms (rash, arthralgias, fever), or depressed serum complement. Recognized secondary causes include infections (HIV, hepatitis B and C, syphilis, malaria, toxoplasmosis, varicella zoster, and reported cases associated with acute COVID-19), drugs and chemicals (NSAIDs, penicillamine, lithium, heavy metals such as mercury and gold, pamidronate, interferon-gamma, and others, each capable of producing histologic patterns resembling membranous nephropathy, minimal change disease, or proliferative glomerulonephritis depending on the agent), malignancy (lymphoma, leukemia), systemic lupus erythematosus, IgA nephropathy, IgA vasculitis (formerly Henoch-Sch\u00f6nlein purpura) nephritis, postinfectious glomerulonephritis, and membranoproliferative glomerulonephritis (also known as complement 3 glomerulopathy). In certain world regions, malaria and schistosomiasis are leading causes of nephrotic syndrome. Congenital nephrotic syndrome, diagnosed within the first 3 months of life, and infantile nephrotic syndrome, diagnosed between 3 and 12 months, most often have a genetic basis, though intrauterine infections (congenital syphilis, toxoplasmosis, CMV, HIV, and others) are also implicated. Podocyte injury underlying nephrotic syndrome can arise from immune-mediated mechanisms, systemic circulating factors (e.g., suPAR), podocyte-intrinsic factors (e.g., ANGPTL4), or genetic variants affecting podocyte structural proteins."
  },
  {
   "title": "Clinical features",
   "content": "Presentation and associated findings differ meaningfully by underlying histology, which helps guide the pretest probability of steroid responsiveness. Minimal change disease typically presents in children ages 2\u20136 (occasionally in adults), with a roughly 2:1 male predominance, nephrotic-range proteinuria in essentially all cases, microscopic or gross hematuria in only 10\u201320%, hypertension in about 10%, and a strong (>80%) response to corticosteroids; complement levels are normal, and urine sediment may show oval fat bodies and granular casts but rarely red cell or leukocyte casts. FSGS typically presents at ages 2\u201310 (occasionally in adults), with hematuria in 60\u201380% of cases, hypertension in about 20% (often early), and steroid resistance in 80\u201385% of cases. Membranous nephropathy is more typical of older patients (often cited around age 40\u201350, though pediatric cases occur), with hematuria in about 60% of cases and an association with venous thromboembolism. Membranoproliferative glomerulonephritis (types I and II) typically presents at ages 5\u201315, with hematuria in about 80% of cases, hypertension in about 35%, and a characteristically decreased C3 level. Across all nephrotic syndrome causes, urinary immunoglobulin losses increase susceptibility to severe infections \u2014 peritonitis, pneumonia, sepsis \u2014 particularly from encapsulated organisms such as Streptococcus pneumoniae and group B streptococcus. A clinically important and sometimes counterintuitive feature: despite visible edema and apparent fluid overload, patients with nephrotic syndrome may actually be intravascularly volume-depleted, which affects fluid management decisions."
  },
  {
   "title": "Complications",
   "content": "Nephrotic syndrome is a hypercoagulable state arising from multiple converging mechanisms: vascular stasis from hemoconcentration and intravascular volume depletion, increased platelet number and aggregability, increased hepatic fibrinogen production, and urinary losses of antithrombotic factors including antithrombin III and protein S. Deep venous thrombosis can occur in any venous bed, including the cerebral venous sinus, renal vein, and pulmonary veins; the clinical risk in children (2\u20135%) is lower than in adults but thrombosis still carries potential for serious consequences and should be watched for actively. Increased susceptibility to serious bacterial infection from encapsulated organisms is a second major complication category, reflecting urinary immunoglobulin losses."
  },
  {
   "title": "Diagnostics",
   "content": "Diagnosis rests on demonstrating the defining laboratory tetrad: heavy proteinuria (>1000 mg/m\u00b2/day or urine protein:creatinine ratio >2), hypoalbuminemia (<3 g/dL), edema, and hyperlipidemia/hypercholesterolemia. Complement levels (C3, C4) help narrow the differential: normal in minimal change disease, FSGS, and membranous nephropathy, but characteristically decreased in membranoproliferative glomerulonephritis. Urine sediment examination can add supportive information \u2014 oval fat bodies and granular casts are typical of minimal change disease, while red cell or leukocyte casts are seldom seen in this entity and, if present, should prompt consideration of an alternative or additional glomerular process. Given how strongly age and clinical features predict the underlying histology (per the demographic and clinical patterns above), many young children with a classic presentation are treated empirically with corticosteroids without an upfront renal biopsy, reserving biopsy for atypical presentations, steroid resistance, or features suggesting secondary disease."
  }
 ],
 "clinical": [
  {
   "title": "Management approach",
   "content": "In a preschool-age child (2\u20136 years) presenting with edema, heavy proteinuria, hypoalbuminemia, and hyperlipidemia, with normal complement and no hematuria/hypertension, minimal change disease is the most likely diagnosis, and a corticosteroid trial is reasonable without upfront biopsy, since more than 80% will respond. Reserve renal biopsy and closer secondary-cause workup for children outside this typical demographic \u2014 age over 12 years, sustained hypertension, significant hematuria, renal dysfunction, extrarenal symptoms (rash, arthralgias, fever), or depressed complement \u2014 since these features shift the differential toward FSGS, membranous nephropathy, MPGN, or a secondary cause such as SLE, IgA vasculitis nephritis, or a triggering infection or drug.\n\nManage the practical complications proactively rather than only treating the proteinuria: monitor for signs of serious bacterial infection (peritonitis, pneumonia, sepsis), particularly from encapsulated organisms, given urinary immunoglobulin losses, and maintain a high index of suspicion for thrombosis (renal vein, cerebral venous sinus, pulmonary veins) given the hypercoagulable state \u2014 even though absolute risk in children (2\u20135%) is lower than in adults, the consequences can be severe. Recognize the paradox of nephrotic syndrome fluid status: a child can be edematous and appear fluid-overloaded while simultaneously being intravascularly volume-depleted, which should inform cautious use of diuretics and fluid management to avoid precipitating or worsening intravascular depletion.\n\nFor a child whose presentation does not fit the classic MCD pattern, or who fails to respond to an appropriate steroid course, pursue biopsy and a secondary-cause workup (infectious serologies, ANA/complement, medication history) rather than continuing empiric steroid therapy indefinitely, since a substantial minority of nephrotic syndrome \u2014 particularly outside the classic 2\u20136-year age range \u2014 reflects FSGS, membranous nephropathy, MPGN, or a secondary systemic process requiring different management."
  }
 ]
}