Autosomal Recessive Polycystic Kidney Disease
Humans normally have 46 chromosomes (tiny, DNA-containing elements) in every cell of the body. DNA encodes genes, which specify all the proteins that make up the body and control its functions.
In humans, there are 23 pairs of chromosomes in cells, with one pair inherited from each parent at conception. Each cell contains 22 pairs of chromosomes, called autosomes, that are the same in males and females. The remaining pair of chromosomes, the X and Y chromosomes, is not shaped similarly, and thus is not matched in the same way as the autosomes.
A genetic disease occurs when one or both parents pass abnormal genes to a child at conception. An "autosomal recessive" genetic disease occurs when each parent passes a defective gene to the fetus during conception.
Mutations in the PKHD1 gene, located on chromosome 6, cause autosomal recessive polycystic kidney disease. Although the function of this gene is not yet known, the protein it makes likely transmits chemical signals from the outside of the cell to the cell's nucleus.
Researchers have not determined how mutations in the PKHD1 gene lead to the formation of numerous cysts and result in the characteristic features of polycystic kidney disease.
When autosomal recessive polycystic kidney disease is inherited, it means an affected person must inherit two altered copies of the PKHD1 gene to be affected by the disorder. Most often, the parents of a child with an autosomal recessive disorder are not affected, but are carriers of one copy of the altered gene.
The chance of this happening (when both parents carry the abnormal gene) is one in four. If only one parent carries the abnormal gene, the baby cannot get autosomal recessive polycystic kidney disease.