Capillary sequencing of the mutated genes identified the causative mutation as a T to A transversion at base pair 88450541 (v38) on Chromosome 7 in the GenBank genomic region NC_000073 encoding Rab38. The mutation corresponds to residue 263 in the mRNA sequence within exon 2 of 3 total exons. The mutation results in a Isoleucine (I) to Asparagine (N) at position 88 (I88N). (J:198554)