Primary Microcephaly (PM) is a neurodevelopmental disorder characterized by a small brain size frequently associated with intellectual disability. CDK5RAP2 is a cyclin-dependent kinase regulatory subunit associated protein whose deficiency causes a rare recessive isolated PM called MCPH3. In this article, Nasser and colleagues report patients carrying new bi-allelic CDK5RAP2 mutations and found that all patients displayed neurosensory defects in addition to PM, including microphthalmia, retinal pigmentation defects, hearing impairments associated with a unique cochlear malformation and hypothalamic anomalies reminiscent of holoprosencephaly. The author conclude that CDK5RAP2 not only governs brain size and that MCPH3 patients should be able to benefit from neurosensory follow-up consistently. (By Dr Sandrine Passemard, https://jmg.bmj.com/content/early/2020/02/03/jmedgenet-2019-106474 )