Autosomal-Dominant (Adult) Polycystic Kidney Disease
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Autosomal-dominant polycystic kidney disease is the most common genetically transmitted renal cystic disease.
The incidence is estimated between 1:500 and 1:1000.
Most patients present in the third to fourth decade of life; however pediatric cases can occur.
Slight male predominance is reported (male-to-female ratio 3:2).
The kidneys are mostly affected bilaterally.
Renal dialysis is the standard of care followed by renal transplant, when necessary.
Renal failure occurs in roughly 59% of patients.
The most frequent clinical findings are positive family history, flank mass, hematuria, hypertension, and azotemia. Hepatic fibrosis and biliary dysgenesis may be present. Renal cell adenoma and carcinoma can be seen among the cysts.
The cysts are lined by a single layer of cuboidal epithelium; however hyperplastic configuration of the epithelium, forming papillary tufts, is focally present. The intervening renal parenchyma may be normal or atrophic. The cysts may contain proteinaceous fluid and calcium oxalate crystals.
PKD1 gene is located on the short arm of chromosome 16 (16p.3.3); codes for polycystin 1, which is involved in cell-cycle regulation and intracellular calcium transport; and localizes in the primary cilia of renal epithelial cells. The PKD2 gene is located on the long arm of chromosome 4 (4q.21.2); codes for polycystin 2, a member of the family of voltage-activated calcium channels; and localizes to the primary cilia of renal epithelial cells. PKD1 is the most commonly implicated, affecting approximately 85% of patients, PKD2 roughly 15%.
Rarely, classic autosomal-dominant polycystic kidney disease is observed associated with tuberous sclerosis, as a new example of the “contiguous gene syndromes,” because the PKD1 gene is immediately adjacent to TSC2 gene, the most important gene of tuberous sclerosis.
The fully developed cases rarely posed a diagnostic problem. However, in the early stages, autosomal-dominant polycystic kidney disease should be distinguished from the other cystic diseases including multiple simple cysts.