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There are three types of polycystic kidney diseases (PKD):

• Autosomal dominant PKD (ADPKD)
• Autosomal recessive PKD (ARPKD)
• Acquired Cystic Kidney Disease (ACKD)

Autosomal Dominant Polycystic Kidney Disease

The term "autosomal dominant" means that a child can inherit a disease or condition if only one of their parents carries the gene for the disease. Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited form of polycystic kidney disease and is responsible for 85-90% of all PKD cases. There are two types of ADPKD:

• Type I
• Type II

Type I is a more severe form than Type II and is associated with earlier age at onset and shorter life expectancy (53 years compared to 69 years)

Symptoms typically develop between the ages of 30 and 40, but can begin in childhood. Fifty percent of patients will develop end-stage renal disease requiring replacement therapy by dialysis or kidney transplant by approximately age 50. This number rises as patients reach their 60's and 70's. Because of its usually late onset, ADPKD has previously been called "adult onset polycystic kidney disease".

Unless otherwise noted, when the term "PKD" is used in the Medifocus Guidebook, it refers to ADPKD.

Autosomal Recessive Polycystic Kidney Disease

The term "autosomal recessive" means that a child can only inherit a disease or condition if both of the parents carry the gene for the disease. Autosomal recessive polycystic kidney disease (ARPKD) is a rare inherited form of the disease with an estimated incidence of 1 per 20,000 people. This type of polycystic kidney disease is an important cause of perinatal death because the kidneys enlarge to such an extent that the lungs cannot function properly after birth. Most of the approximately 50-60% of children who survive develop renal failure and liver fibrosis often in the first decade of life. Because of this early onset of symptoms, this form of PKD has previously been called "infantile PKD".

Acquired Cystic Kidney Disease

Acquired cystic kidney disease (ACKD) is not inherited, but develops most commonly in patients who have been on long-term dialysis treatment. Approximately 90% of people with ACKD have been on dialysis for 5 years or more. They have an increased chance of also developing kidney cancer.