Editor—Autosomal dominant polycystic kidney disease (ADPKD) is a multisystem disease with intrafamilial phenotypic heterogeneity. Cerebral aneurysms develop in 10-20% of patients with ADPKD.1 2 Aneurysm rupture may precede the development of hypertension or renal manifestations of the disease.2 Two ADPKD loci (PKD1 andPKD2) map to chromosomes 16p and 4q, respectively. Reports of unlinked pedigrees have suggested the existence of a third unmapped locus.3-7 We report a three generation white family with an ADPKD like disease, unlinked to thePKD1 or PKD2 loci (fig 1, table 1). Other genetic causes of renal cysts, such as tuberous sclerosis and von Hippel-Lindau disease, have been excluded clinically and linkage to the known loci for these diseases is unlikely. This family supports the case for a third locus for ADPKD, but differs from the previously described unlinked pedigrees by its presentation with cerebral aneurysm rupture.

Ethical approval for this study was granted by the local research ethics committee. The family was identified because three members had sustained a subarachnoid haemorrhage. All family members who were older than 18 were invited for examination and screening for intracranial aneurysms by magnetic resonance angiography (MRA). There was no clinical evidence of tuberous sclerosis, von Hippel-Lindau disease, or autosomal recessive polycystic …