Some important concepts to understand the glomerular diseases

A variety of histologic patterns can produce diverse clinical syndromes; thus, for example, nephritic syndrome and hematuria can be produced by membranoproliferative glomerulonephritis (GN), diffuse endocapillary proliferative GN (acute), IgA nephropathy (or Berger’s disease), and so on. A nephrotic syndrome (NS) can be produced by several diseases: membranous GN, focal and segmental glomerulosclerosis, minimal change disease, amyloidosis, diabetic nephropathy, and others.

• In a disease different patterns of pathologic changes can be seen; for example, in lupus may appear only mesangial changes, diffuse endocapillary proliferation, membranoproliferative-like lesions, membranous pattern, or focal segmental (chronic) lesions. This variability in the morphologic expression has given origin to the classification of lupus nephritis.

• A type of pathologic change can be caused by several diseases: for example, a membranoproliferative pattern can be seen in lupus, infections, hepatitis and cryoglobulinemia.

• The changes found in a renal biopsy rarely are specific of a disease; for example, in some hereditary diseases like Alport syndrome and Anderson-Fabry disease.

• Therefore the renal diagnosis is a process that integrates the clinical information, laboratory data, morphology and immunopathology to reach the “better diagnosis”.

• Different diseases can have a same pathogenic mechanism; for example, crescentic GN can be seen in lupus, acute GN, anaphylactoid purpura, IgA nephropathy, and in all these conditions the formation mechanism of crescents is related to rupture of glomerular capillary walls with protein passage to the Bowman’s space.