Inherited and congenital diseases
A very large polycystic kidney (left) next to a normal kidney (right)
Polycystic kidney disease
Polycystic kidney disease (PKD) is the commonest inherited disease causing end stage renal failure (ESRF), and accounts for up to 8% of patients on RRT programmes. The major variety is an autosomal dominant disorder (ADPKD) said to affect 80/100,000 of the population. The kidneys become slowly enlarged and contain many fluid-filled cysts. There may be hypertension, haematuria, abdominal discomfort, or no symptoms at all.
Only about 50% of individuals with PKD1 mutations progress to ESRF, and those with mutations in PKD2 tend to have milder disease with less and later renal failure.
Cysts may not be detectable by ultrasound until affected individuals are in their 20s or even later. There may also be hepatic cysts, and there is also an increased incidence of subarachnoid haemorrhage and some other abnormalities. Cysts may bleed and become infected, and there is an increased incidence of renal stones and UTIs.
No management strategy has yet been shown to affect the rate of renal deterioration, though drug trials are commencing. Hypertension should be treated. Patients with PKD do well on dialysis and after renal transplantation, but if kidney enlargement is massive, nephrectomy is sometimes required to make space for transplantation.
Alport syndrome
The second most common inherited cause of kidney failure, usually X-linked and affecting young men. Autosomal recessive disease may also occur and is clinically indistinguishable. Caused by mutations in any of three tissue-specific basement membrane collagen genes. These collagens are an important part of glomerular basement membrane (GBM) and the cochlea. Their genes are called COL4A5 (X chromosome), COL4A3 and COL4A4.
Typically affected males develop progressive haematuria, proteinuria, then renal failure and deafness in their teens, and ESRF in their twenties. Carriers often have haematuria and the renal biopsy finding of a thin GBM. A proportion of carriers may develop serious renal disease in later life.
Renal hypoplasia
There are many other inherited renal disorders, but the largest group comprises conditions in which renal development is incomplete or imperfect. Unilateral renal agenesis (having a single normal kidney) is quite common and asymptomatic. If the kidney is normal, it will hypertrophy as you grow and provide adequate renal function. If it's damaged, it may not. Renal hypoplasia overlaps with other developmental or structural disorders, notably reflux nephropathy.
Further info
- Patient info on PKD
- Patient info on Alport syndrome
- Genetics from Medpedia. The videos are excellent, but the article is good too.
- A primer on genetics from the Wellcome Trust's human genome pages : see the individual links to dominant, recessive and X-linked diseases, and more.
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