Randomized clinical trial of long-acting somatostatin for autosomal dominant polycystic kidney and liver disease

There are no proven, effective therapies for polycystic kidney disease (PKD) or polycystic liver disease (PLD). We enrolled 42 patients with severe PLD resulting from autosomal dominant PKD (ADPKD) or autosomal dominant PLD (ADPLD) in a randomized, double-blind, placebo-controlled trial of octreotide, a long-acting somatostatin analogue. We randomly assigned 42 patients in a 2:1 ratio to octreotide LAR depot (up to 40 mg every 28+/-5 days) or placebo for 1 year. The primary end point was percent change in liver volume from baseline to 1 year, measured by MRI. Secondary end points were changes in total kidney volume, GFR, quality of life, safety, vital signs, and clinical laboratory tests. Thirty-four patients had ADPKD, and eight had ADPLD. Liver volume decreased by 4.95%+/-6.77% in the octreotide group but remained practically unchanged (+0.92%+/-8.33%) in the placebo group (P=0.048). Among patients with ADPKD, total kidney volume remained practically unchanged (+0.25%+/-7.53%) in the octreotide group but increased by 8.61%+/-10.07% in the placebo group (P=0.045). Changes in GFR were similar in both groups. Octreotide was well tolerated; treated individuals reported an improved perception of bodily pain and physical activity. In summary, octreotide slowed the progressive increase in liver volume and total kidney volume, improved health perception among patients with PLD, and had an acceptable side effect profile.

Incompletely penetrant PKD1 alleles suggest a role for gene dosage in cyst initiation in polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) caused by mutations in PKD1 is significantly more severe than PKD2. Typically, ADPKD presents in adulthood but is rarely diagnosed in utero with enlarged, echogenic kidneys. Somatic mutations are thought crucial for cyst development, but gene dosage is also important since animal models with hypomorphic alleles develop cysts, but are viable as homozygotes. We screened for mutations in PKD1 and PKD2 in two consanguineous families and found PKD1 missense variants predicted to be pathogenic. In one family, two siblings homozygous for R3277C developed end stage renal disease at ages 75 and 62 years, while six heterozygotes had few cysts. In the other family, the father and two children with moderate to severe disease were homozygous for N3188S. In both families homozygous disease was associated with small cysts of relatively uniform size while marked cyst heterogeneity is typical of ADPKD. In another family, one patient diagnosed in childhood was found to be a compound heterozygote for the PKD1 variants R3105W and R2765C. All three families had evidence of developmental defects of the collecting system. Three additional ADPKD families with in utero onset had a truncating mutation in trans with either R3277C or R2765C. These cases suggest the presence of incompletely penetrant PKD1 alleles. The alleles alone may result in mild cystic disease; two such alleles cause typical to severe disease; and, in combination with an inactivating allele, are associated with early onset disease. Our study indicates that the dosage of functional PKD1 protein may be critical for cyst initiation.

Molecular diagnostics of Meckel-Gruber syndrome highlights phenotypic differences between MKS1 and MKS3

Meckel-Gruber syndrome (MKS) is a recessively inherited, lethal disorder characterized by renal cystic dysplasia, occipital encephalocele, polydactyly and biliary dysgenesis. MKS is genetically heterogeneous with three loci mapped and two identified; MKS1 (17q23) and MKS3 (8q22.1). MKS1 is part of the Finnish disease heritage, while MKS3 has been described exclusively in consanguineous Asian families. Here we aimed to establish molecular diagnostics for MKS, determine the importance of MKS1 and MKS3 in non-consanguineous populations, and study genotype/phenotype correlations. The coding regions of MKS1 and MKS3 were screened for mutations by direct sequencing in 17 families clinically diagnosed with MKS in the US or The Netherlands. The clinical phenotype was compared to genic and allelic effects. Both mutations were identified in ten families; five MKS1 and five MKS3. All but two were compound heterozygotes, consistent with their non-consanguineous nature. The MKS1-Fin(major) mutation accounted for 7/10 MKS1 mutations; two novel changes were additionally detected. Seven novel mutations were found in MKS3, including three missense changes. We concluded that MKS1 and MKS3 account for the majority of MKS in non-consanguineous populations of European origin. Polydactyly is usually found in MKS1 but rare in MKS3. Cases with no, or milder, CNS phenotypes were only found in MKS3; hypomorphic missense mutations may be associated with less severe CNS outcomes. This study is consistent with further genetic heterogeneity of MKS, but underlines the value of molecular diagnostics of the known genes to aid family planning decisions.