PRR12 and Global developmental delay: The dark gene Proline-Rich Protein 12 (PRR12) has been recently identified in a cohort of young age patients as the cause of a complex and heterogeneous phenotype characterized by global developmental delay and developmental abnormalities mainly affecting the brain and the eye, such as microcephaly, microphtalmia/anophtalmia and iris coloboma [7,8,9,10].