Polycystic kidney disease has two specific variants called autosomal recessive polycystic kidney disease and autosomal dominant polycystic kidney disease. Both are caused by different genes and produce slightly different diseases. Both can be diagnosed through ultrasound imaging or CT scan. Distinguishing between the two is easy because they affect different age groups.
ARPKD
The PKD Foundation explains that autosomal recessive polycystic kidney disease, or ARPKD, is caused by a PKHD gene which is found on chromosome 6. The PKHD gene is recessive. If both parents are carriers of this disease, there is a 25 percent chance that each conception will have the disease. Approximately 1 in 20,000 people are affected by ARPKD. According to the ARPKD/CHF Alliance, Finns and Afrikaaners are more likely to be born with ARPKD.
ARPKD is often diagnosed through prenatal ultrasound. Approximately 50 percent of newborns born with this disease don't make it past infancy. However, babies that survive these treacherous first months stand a good chance of thriving.
ADPKD
According to the PKD Foundation, autosomal dominant polycystic kidney disease can be caused by either the PKD1 gene on chromosome 16 or the PKD2 gene on chromosome 4. If one parent has one of these genes, there is a 50 percent chance that each offspring will have ADPKD.
The NYU Division of Nephrology reports that this is "the most common, life-threatening single-gene disease," affecting 500,000 people in the U.S and 12 million worldwide. Unlike ARPKD, ADPKD is often not diagnosed until the patient is in his 30s or 40s. The National Institute of Diabetes, Digestive and Kidney Disease notes that many times the disease goes undetected and some people live for many years not knowing that they have ADPKD.
Related Disorder
Renal dysplasia is not classified as a polycystic kidney disease, but it also produces cysts. The National Institute of Diabetes, Digestive and Kidney Diseases notes that renal dysplasia is a developmental disorder in which the kidneys do not form properly. At least some of the tiny filters in the kidney called glomeruli are not connected to collecting ducts so urine has nowhere to go. Urine remains backed up at the glomeruli, where it forms cysts.
Like ARPKD, renal dysplasia can often be diagnosed through prenatal ultrasound. In many instances, it only affects one kidney so renal problems may not be pronounced until the child is older.
