Nephrotic syndromeN04.9

The nephrotic syndrome in adults is defined as the "occurrence of proteinuria of >3.0-3.5g/dl"; in children the nephrotic syndrome is defined as the occurrence of "large" proteinuria (≥ 40 mg/m² body surface area (KOF)/h or ≥ 1 g/m² KOF/day) and hypalbuminemia (< 25 g/l) in serum" (Downie ML et al. 2017).

Furthermore, the nephrotic syndrome is defined by the following clinical symptoms:

• hypoproteinemia
• Hypalbuminemic edema
• Secondary hyperlipidemia in the form of an increase in total and LDL cholesterol, in severe cases also in triglycerides.

A distinction is made between:

• idiopathic (primary)

and

• symptomatic (secondary) forms of the nephrotic syndrome. The symptomatic nephrotic syndrome is associated with numerous underlying diseases.

Nephrotic syndrome is predominantly due to acquired damage to the glomerular basement membrane, leading to increased permeability to plasma proteins and proteinuria (in X-linked Alport syndrome, a mutation of collagen IV is present, leading to a defect in the lamina densa of the glomerular basement membrane and proteinuria).

The following diseases are characterized by nephrotic syndrome:

• Glomerular minimal lesions = minimal-change glomerulopathy (MCD =minimal change disease) (N05.0).
• Focal segmental glomerulosclerosis (N05.1)
• Membranous glomerulonephritis (N05.2)
• Membran0proliferative glomerulonephritis (N05.5)
• Diabetic nephropathy
• Rare causes such as: C3 glomerulopathy, plasmocytoma, systemic amyloidosis, renal vein thrombosis.

In most cases, the symptoms of the triggering underlying disease determine the overall clinical symptoms! In this respect, the clinical picture of proven nephrotic syndrome is inhomogeneous. Possible consequences of pathological glomerular proteinuria are:

• Acquired IgG deficiency (loss of IgG due to proteinuria) with consecutive tendency to infection
• Symptoms of renal insufficiency, possibly with hypertension
• Thromboembolic events (anthrombin loss; Barbano B et al. 2013)

Albumine↓ gamma-Globuline↓ with relative increase of alpha2 and beta globulins (↑)

For renal failure:

• Creatinine ↑ Urea ↑; Creatine clearance ↓
• IgG ↓ Antithrombin ↓
• Cholesterin↑ Triglyzeride↑

• Clinical sympotmatics
• Imaging procedures (sonography of the kidneys)
• Renal biopsy (clarification of the underlying disease; Yokoyama H et al. 2012)

Therapy of the underlying disease or elimination of possible toxic causes.

Symptomatic therapy:

• Physical protection
• Diet: Low protein and low salt diet
• Diuretic therapy (combination of potassium-saving diuretic + thiazide)

1. Barbano B et al (2013) Thrombosis in nephrotic syndrome. Semin Thromb Hemost 39:469-476.
2. Davin JC (2016) The glomerular permeability factors in idiopathic nephrotic syndrome. Pediatric nephrol 31:207-215.
3. Downie ML et al (2017) Nephrotic syndrome in infants and children: pathophysiology and management. Paediatr Int Child Health. 37:248-258.
4. Nishi S et al (2016) Evidence-based clinical practice guidelines for nephrotic syndrome 2014, Clin Exp Nephrol 20:342-370.
5. Yokoyama H et al (2012) Renal disease in the elderly and the very elderly Japanese: analysis of the Japan Renal Biopsy Registry (J-RBR).Clin Exp Nephrol 16:903-920.