Most cases result in stillbirth or early neonatal death (40%); encountered in 1:20,000 live births.
Associated with gene PKHD1 that maps to chr region 6p21-p12 and encodes for protein fibrocystin located in cilium; >300 mutations in PKHD1 identified.
Mutations in PKHD1 are detected in 80-85% of cases.
Enlarged cystic kidney at birth.
Bilaterally enlarged kidneys with "radial rays" of cysts oriented perpendicular to the cortex (image A).
Reniform shape is generally maintained.
Ureters are normal.
Cystic dilatation of cortical and medullary collecting ducts +/- involvement of PCT and Bowman's capsule (image B).
Nephrons between dilated ducts are normal (vs. renal dysplasia).
Autosomal recessive inheritance; hepatic lesions mimicking congenital hepatic fibrosis may also be present (older patients develop hepatosplenomegaly and portal hypertension).
Lethal neonatal form: massively enlarged kidney and small hypoplastic lung.
Infantile childhood form: smaller kidneys and larger lungs and congenital hepatic fibrosis.
Lethal in neonates; good prognosis if neonate survives 1st month of life (90% 5 years survival).
50% of children will have systemic hypertension and renal insufficiency.