Brain imaging identified a Chiari malformation Type I. Subsequent exome sequencing identified two frame-shift mutations in ARID1B in close proximity (c.5151del and c.5153del), both resulting in a premature stop codon in the 48th amino acid downstream of the mutation (p.Lys1718Argfs*48). The gene discussed is ARID1B; the disease is Chiari malformation type I.