Acrocallosal syndrome is characterized by postaxial polydactyly, macrocephaly, agenesis of the corpus callosum, and severe developmental delay. In a few patients with this disorder, a mutation in the KIF7 gene has been reported, which was associated with impaired GLI3 processing and dysregulaton of GLI3 transcription factors. A single patient with acrocallosal syndrome and a de novo p.Ala934Pro mutation in GLI3 has been reported, whereas diverse and numerous GLI3 mutations have also been described in syndromes with overlapping clinical manifestations, including Greig cephalopolysyndactyly syndrome, Pallister–Hall syndrome, trigonocephaly with craniosynostosis and polydactyly, oral–facial-digital syndrome, and non-syndromic polydactyly. Here, we describe a second patient with acrocallosal syndrome, who has a de novo, novel c.2786T > C mutation in GLI3, which predicts p.Leu929Pro. This mutation is in the same domain as the mutation in the previously reported patient. These data confirm that mutations in GLI3 are a cause of the acrocallosal phenotype. © 2013 Wiley Periodicals, Inc.