Nephritic syndrome is characterized by inflammation of the glomeruli and includes the following clinical features: hematuria, hypertension, oliguria, and less than 3.5 grams per day of proteinuria. Patients with nephritic syndrome also commonly present with red cell casts in the urine and azotemia. Nephritic syndrome can be caused by several diseases including Alport syndrome, Berger's disease, poststreptococcal glomerulonephritis and rapidly progressive glomerulonephritis.
This disease is inherited as an X-linked trait in approximately 85% of cases. It is commonly called X-linked dominance because males express the full syndrome while female carriers can have manifestations of disease like hematuria. Alport syndrome can also be inherited in an autosomal recessive fashion, as well as autosomal dominant manner in about 5% of cases.
Alport syndrome is caused by a mutation in type IV collagen, which is an important structural component of basement membranes present in the kidney, eyes, and ears.
Progression of the disease leads to thinning of the basement membrane with a split lamina densa.
On microscopy, the split basement membranes in Alport syndrome show irregular thinning and thickening, described as a lamellated "basket weave" appearance.
Various ocular disorders are a major component of Alport syndrome because type IV collagen is abundant in the ocular system. Manifestations include posterior cataracts and corneal dystrophy. A pathognomonic ocular feature of Alport syndrome is anterior lenticonus.
Difficulty hearing results because type IV collagen is an essential piece of the auditory system. Type IV collagen is a crucial component of the cochlea in the ear. Therefore, a mutation in type IV collagen can cause deafness, which is a major component of Alport syndrome. However, auditory defects may be subtle as well.
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