Clinic and morphologic findings through light and electronic microscopy scanning are related to that which is described as CG or Type III Collagen Glomerulopathy. CG has occurred both occasionally and within families. The cases with family background have shown the possibility of treating an autossomic recessive inherited disease [6
]. The etiopathogenesis of this disease has been mentioned since the beginning of the cited publications, and it has also questioned CG as being a systemic disease or even only a variation that might come from glomeruli cells [8
]. There is neither family background of the disease nor evidence of systemic diseases in any of the three reported cases. They presented some factors in common, such as sex, age (teenagers and young adults) and the presence of non-nephrotic proteinuria associated with microscopic hematuria.
The CG was initially considered a clinical variant of Nail-Patella Syndrome, but morphologic changes are different, and clinical findings and family studies have excluded this hypothesis. In contrast to Nail-Patella Syndrome glomerulopathy, diffuse glomerular changes are universally observed by light microscopy. They consist of marked enlargement of the glomerular tuft resulting from both expansion of the mesangial matrix and thickening of the cappillary walls [4
], as observed in the three cases presented. The lesion may mimic diffuse thrombotic microangiopathy, or it may resemble type I membranoproliferative glomerulonephritis if mesangial hypercellularity is associated [6
]. However, the hallmark of the disease is the presence of type III fibrillar collagen in the glomerular extracellular matrix observed by Electronic microscopy, and other differential diagnosis still may be established by immunofluorescence.
The findings under immunofluorescence microscopy to immunoglobulins and components of the complement are usually negative, when it comes to CG, as showed in the second case. Literature describes that conventional immunofluorescence is negative or shows focal non-specific deposits of immunoglobulins, mainly IgM, and complement components [4
]. In the third case, IgM was positive in capillary walls; however, sparse positivity of IgM, IgG, C3 and other immunoreagents had already been reported which probably represents a flood of plasmatic proteins [9
Picrosyrius staining was initially described in 1964 and it has been used to detect collagen in many tissues, including kidneys, and it is specific for type I and type III collagen. The red of Syria (component of the Picrosyrius) is a long coloring molecule which penetrates the folds of the collagen molecules and becomes birefrigent when observed under polarized light microscopy. Under standard microscopy light, it changes the color of the collagen into red and under polarized light, it exhibits a yellow-orange birefringence [10
]. The picrosyrius staining, which was presented in the second case, showed the presence of reddish material in the mesangium, when it was seen under standard microscopy; however, when it was seen with birefringence, it became greenish under polarized light, which shows the collagen found in this area of the glomerulus. Picrosyrius staining has been used to study interstitial fibrosis and it seems to be useful in identifying collagen in the glomerulus, and also in helping the diagnosis of other glomerulopathies.
Electronic microscopy scanning is essential in the definitive diagnosis. In the majority of cases, the ultra structural findings provide evidence of collagen III. The fibers are in the mesangium and in the subendothelial space, but not in the subepithelial compartment or inside the basement membrane [12
], as opposed to Nail-Patella syndrome in which the type III collagen is only inside of the basement membrane. In all three reported cases, the identification of CG was made through electronic microscopic scanning, and curved and disorganized fibers were found, which also created irregular bunches when they were cut lengthwise and with the shape of snakes or commas when the same were transversely cut. These ultra structural features distinguish the fibers of the collagen III from the fibers of regular collagen, which usually look like straight lines when cut lengthwise, and the same fibers look like circles when transversely cut.