Ciliopathies are a group of disorders caused by primary cilium dysfunction and characterized by substantial genetic and phenotypic heterogeneity. Establishing genotype-phenotype correlations is critical for directing clinical genetic testing, informing medical management, and interpreting variants identified by genome-wide sequencing technologies. This study reports the spectrum of CC2D2A mutations in CC2D2A-related Joubert syndrome and identifies an enrichment for brain imaging abnormalities (particularlry ventriculomegaly) and seizures in these patients compared to Joubert syndrome as a whole. (By Ruxandra Bachmann-Gagescu, http://jmg.bmj.com/content/49/2/126 )