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At a glance

Genetic disorder defined by the pathological development of fluid-filled cysts throughout the kidneys leading to organ enlargement and chronic kidney disease. The morbidity associated with the most common forms, autosomal dominant PKD (ADPKD) and autosomal recessive PKD (ARPKD), is mostly limited to the kidney and liver and extends from neonates to old age.

Synonym

PCKD Syndrome.

Classification

Numerous polycystic kidney disease classifications have been described (see Table P-1).

TABLE P-1Classification of Polycystic Kidney Disease

Incidence

Highly variable estimates. 1:400 to 1:20,000 live births overall. The age distribution of cases has two peaks, one at birth and one between the ages of 30 and 60 years.

Genetic inheritance

Autosomal dominant polycytic kidney disease (ADPCK) is caused by mutations in two genes: PKD1 (accounts for 80-85% of patients) and PKD2 (accounts for 15-20%). ARPKD is a neonatal disease caused by mutation in one gene: PKHD1 on chromosome 6p21. Both sexes are affected. Syndromic PKD are caused by a variety of mutations.

Pathophysiology

Polycystin-1 interacts with polycystin-2, which is a nonselective calcium-permeable channel. Both, polycystin-1 and 2 localize to primary cilia, which trigger intracellular calcium transients upon mechanical stimulation or ligand binding. The PKHD1 gene encodes for fibrocystin and has been localized in primary cilia, as well as to the basal body. It may mediate its activity through polycystin-2. The mutations in PKD1 and PKD2 lead to dysfunction of polycystin-1 and 2 resulting in aberrant cellular signaling pathways with increased or disorganized cell growth and fluid secretion that results in fluid accumulation and cyst formation.

Diagnosis

Ultrasonography is the best diagnostic tool, and in late pregnancy can allow presumptive in utero diagnosis in most cases (increased echogenicity and renal enlargement). The feasibility and reliability of DNA obtained by amniocentesis or chorionic villus sampling during prenatal testing is being examined. Hepatic involvement is invariable with generalized portal and interlobular fibrosis, and bile duct proliferation. The remainder of the hepatic parenchyma is normal.

Clinical aspects

One of the notable features ...

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