Molecular Test Detection

Test : Adult Polycystic Kidney Disease DNA detection


Indications : A genetic test for PKD is ordered for the following reasons:

• To confirm autosomal dominant or recessive disease in a patient to plan treatment
• To detect the disease prenatally through amniocentesis in a fetus of carrier parents

Blood is collected from the patient and the DNA is isolated, fragmented and allowed to run through a gel electrophoresis. Depending on its weight the DNA fragments are spread on the gel. This is then transferred to a special blotting paper, denatured and fixed. This denatured DNA is exposed to fluorescing probes which can then be detected using fluorescent techniques. This method is known as Southern blotting.

Physiology : Polycystic kidney disease (PKD) is a genetic condition affecting the kidneys, which are organs that filter blood and discard the waste through urine. It is widely known that mutations in the PKD genes cause the disease, but how it occurs is poorly understood.

As the name suggests, PKD is characterized by the growth of multiple cysts in the kidneys. This causes fluid formation in the kidneys and they become large and impaired.

An affected person requires dialysis and eventually kidney transplantation without which the condition will progress to kidney failure or end-stage renal disease (ESRD) which is fatal.

There are two inherited forms of PKD:

• Autosomal dominant PKD - This is the most common inherited form (90% of those with PKD). The majority inherit from a parent, while in some it is a spontaneous occurrence. The symptoms usually develop after 30 but it can appear earlier too.

• Autosomal recessive PKD - This is a rare form of PKD and the symptoms begin from birth.

Mutation in 3 genes-polycystic kidney disease or polycystin (PKD) 1, PKD2, or PKD3-are associated with adult polycystic kidney disease. In majority of the cases the affected gene is located on short arm of chromosome 16(16p).

Interpretation : Specific mutations in the PKD gene indicate polycystic kidney disease in a person. In some cases, it indicates a carrier state.

Sample : Laboratory generally provides an interpretive report.

Test Method : Southern blotting technique.

Related Tests : Blood, amniotic fluid, chorionic villus, tissue

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