High level albuminuria and the nephrotic syndrome are pathognomonic of glomerular renal disease and must be distinguished from other high-level proteinuria. Causes of the nephrotic syndrome are numerous and its clinical significance requires diagnostic rigor to propose targeted treatment and prevent possible complications and renal functional decline. A nephrotic syndrome can also be an early expression of potentially severe non-renal medical conditions. It should be considered in any patient with edema, regardless of age and comorbidities.