Alport syndrome, recessive type

Alport Syndrome, Recessive Type

Alport syndrome is a genetic disorder characterized by kidney disease, hearing loss, and eye abnormalities. The recessive type of Alport syndrome is one of the forms of this condition, which is inherited in an autosomal recessive manner.

Genetics

Alport syndrome is caused by mutations in genes that are responsible for the production of type IV collagen, a crucial component of basement membranes in the kidneys, ears, and eyes. The recessive type of Alport syndrome is typically associated with mutations in the COL4A3 or COL4A4 genes. These genes encode the alpha-3 and alpha-4 chains of type IV collagen, respectively.

In the recessive form, an individual must inherit two copies of the mutated gene, one from each parent, to manifest the disease. Parents of an affected individual are usually carriers, meaning they have one normal and one mutated gene but do not show symptoms of the disease.

Clinical Features

The clinical presentation of Alport syndrome, recessive type, includes:

• Kidney Disease: Progressive renal failure is a hallmark of Alport syndrome. Patients often develop hematuria (blood in urine) and proteinuria (protein in urine) in childhood, which can progress to end-stage renal disease (ESRD) in adolescence or early adulthood.

• Hearing Loss: Sensorineural hearing loss is common and typically develops in late childhood or early adolescence. It is usually bilateral and progressive.

• Eye Abnormalities: Patients may have anterior lenticonus (a conical protrusion of the lens surface), which can lead to visual impairment. Other ocular findings can include retinal flecks and corneal dystrophy.

Diagnosis

Diagnosis of Alport syndrome, recessive type, is based on clinical findings, family history, and genetic testing. A kidney biopsy may show characteristic changes in the glomerular basement membrane, such as thinning, splitting, and lamellation.

Genetic testing can confirm the diagnosis by identifying mutations in the COL4A3 or COL4A4 genes.

Management

There is no cure for Alport syndrome, but management focuses on slowing the progression of kidney disease and addressing hearing and vision problems. Angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) are often used to manage proteinuria and hypertension, which can help delay the onset of ESRD.

Hearing aids or cochlear implants may be necessary for managing hearing loss, and regular ophthalmologic evaluations are recommended to monitor and treat eye abnormalities.

Prognosis

The prognosis for individuals with Alport syndrome, recessive type, varies depending on the severity of the kidney disease and the age at which ESRD develops. With advances in renal replacement therapy, such as dialysis and kidney transplantation, the life expectancy of affected individuals has improved.

Also see

• Alport syndrome
• COL4A3
• COL4A4
• End-stage renal disease
• Sensorineural hearing loss