Autosomal Recessive Polycystic Kidney Disease is different from Autosomal Dominant Polycystic Kidney Disease. They are different disease processes with bilateral (two) cystic kidneys in common. Large cysts (macrocysts) are associated with ADPKD, located at any point along the nephron. Macrocysts have been found in ARPKD, but usually microcysts (less than 2 cm) are present and are located in the collecting tubules.
Relative renal size decreases with age in ARPKD, yet increases in ADPKD. Both are inherited disorders, but the inheritance patterns are different. The most commonly used prevalence rate is 1:400 to 1:1000 for ADPKD and 1:6,000 to 1:40,000 for ARPKD. ADPKD is passed on 50% of the time from one affected parent (parent with disease) with ~10-30% resulting from a spontaneous mutation and is considered a systemic disease, affecting a variety of different organs in different ways; ESRD is reached 50% of the time by 60 years of age.
As previously noted ARPKD is passed on 25% of the time with each pregnancy where both parents are “silent” carriers of a mutated gene. The child must receive a mutated gene from each parent for disease expression. Parents of children with recessive disorders are unaffected by the disease, or disease free, and there is a 50% chance that unaffected ARPKD/CHF full-siblings will be carriers of the mutated gene and 25% chance they will neither carry nor have the disease. When a person is only a carrier and has children with someone who is not a carrier, then there is a 50% chance each child will be a carrier and a 50% chance they will not be a carrier. If an individual with ARPKD has children with someone who neither has ARPKD nor carries the mutated gene, then all their children will be carriers of the “silent” gene. If an ARPKD individual has children with someone who carries the gene, with each pregnancy there is a 50% chance the child will carry the gene and 50% chance they will have the disease. If two ARPKD individuals have children, then there is a 100% probability that all their children will have ARPKD.