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Alport syndrome (AS) is a disease caused by abnormal collagen formation, which occurs in about 1 in 50,000 newborns. It affects both males and females, but can be inherited only from females in the majority of cases. It affects the kidneys, and inevitably results in progressive renal fibrosis, and end-stage renal failure.
Patients with Alport syndrome may present with:
On examination, there may be:
The disease is due to mutations in the COL4A5, COL4A3 or COL4A44 genes which code for type IV collagen synthesis and assembly. This defect causes immature glomerular basement membrane to persist in the kidneys, leading to failure of blood filtration. The occurrence of hematuria and proteinuria is a consequence of the membrane defect, and the ultimate outcome is kidney damage.
The genetic basis of the disease makes family genetic testing necessary. Alport syndrome is inherited mostly as an X-linked disorder, but in some cases it is autosomal recessive, and in very rare cases autosomal dominant. Early detection of the mutation may help to prevent or delay the onset of renal failure, and to detect carrier mothers, who are at a higher risk of renal complications themselves.
The features of Alport syndrome are:
Females may never have any symptoms other than hematuria, while affected males usually show the full range of disease.
Genetic testing is the gold standard for diagnosis of the condition. Each of these mutations points to a distinct mode of inheritance, as well as a quantified risk for the early onset of renal failure, and for the occurrence of extra renal manifestations.
Other tests include audiometry, renal function tests, renal biopsy and urine analysis.
Management involves genetic testing and counseling, and measures to protect the kidneys, the hearing and the vision. Angiotensin-converting enzyme (ACE) inhibitors, angiotensin-receptor blockers (ARB) and aldosterone inhibitors are all useful in the management of proteinuria in this condition. Lens replacement is often necessary.