Overview
Collagen III nephropathy is a glomerular disease characterized by the deposition of type III collagen fibers in the glomerulus, also known as type III collagen glomerulopathy and collagen fibrous glomerulopathy, with a wide range of age of onset, no gender differences, and family aggregation in some cases.
Etiology
It is not clear, there is no type III collagen in the glomeruli of normal people, and the large amount of type III collagen in the glomeruli of patients may be related to heredity, and in familial cases, the mode of inheritance is characterized by autosomal recessive hereditary disease.
Symptoms
Often manifested as proteinuria, some patients have large amount of proteinuria, hypoproteinemia, high degree of edema, hyperlipidemia and other manifestations of nephrotic syndrome, 1/3 of patients have hypertension manifestations, hematuria is rare. Physical examination may have generalized depressed edema.
Examination
1. Laboratory examination
(1) Blood biochemistry: plasma albumin decreases, cholesterol and triacylglycerol increase.
(2) Urine routine: elevated urinary protein.
2. Histopathologic examination
Under light microscope, cell proliferation is rare, immunofluorescence shows focal segmental deposition of immunoglobulin IgG and IgM, and type III collagen fiber staining is strongly positive in the inner basement membrane of glomerular capillaries and the mesangial area, while only type IV collagen is found in the normal glomerulus, and type III collagen is usually only found in the renal interstitium and the wall of small blood vessels in normal conditions. Electron microscopy showed a large number of thick collagen fibers arranged in bundles in the inner lax layer of the glomerular capillary basement membrane and the tunica albuginea region.
Diagnosis
The age range of onset of the disease is wide, from infancy to adulthood, with no gender difference, and some cases show family aggregation. Common clinical manifestations include proteinuria, edema, and nephrotic syndrome in some patients, with normal or mildly abnormal renal function. Because of the lack of specificity in clinical manifestations and laboratory tests, the diagnosis is mainly based on pathology, immunofluorescence or immunohistochemistry which confirms that there are a large number of type III collagen fibers deposited or typical changes in electron microscopy, which can be a confirmation of the diagnosis.
Differential diagnosis
1. Nail-patella syndrome
It is an autosomal dominant disease with a young age of onset, accompanied by nail and patellar dysplasia. Pathologic examination shows that there are collagen fibers deposited in the dense layer of the capillary basement membrane, but there is a mixture of type I, type III and type IV collagen.
2. Fibrous glomerulopathy
The clinical manifestations of this disease are similar to those of this disease, but the pathologic phenotypes are diverse, and can be manifested as membranoproliferative, membranous, or thylakoid proliferative pathologic types. Immunofluorescence is often IgG and other strong positive, electron microscopy can be seen in the diameter of 20nm arranged disorganized fiber-like material deposits, the site is not sure, and collagen Ⅲ nephropathy has obvious difference.
3.Fibronectin glomerulopathy
Hereditary glomerulopathy, the clinical manifestation is similar to this disease, light microscopy can see a large number of homogeneous protein-like material in the endothelium of the basement membrane of the tethered zone and capillaries, immunopathological examination shows that fibronectin is strongly positive, electron microscopy can see a large number of granular and fibrous material deposits in the tethered zone and the endothelial side of the basement membrane.
Treatment
There is no specific treatment for this disease, and glucocorticoids, cytotoxic drugs and anticoagulants are not effective.
Prognosis
The disease progresses gradually and the prognosis is poor.