PKD2 and Dilatation of the cerebral artery: Polycystin 1 has been implicated in the structural integrity of blood vessels, providing a plausible genotype-phenotype mechanism for SCAD and potentially a useful paradigm to aid understanding of the coronary biomechanical processes leading to SCAD.23,24 The involvement of PKD1 but not PKD2 may be explained by the known milder phenotype, especially in females of PKD2 where renal disease occurs later and fewer intracranial aneurysms are reported.