TBC1D24 and deafness-onychodystrophy syndrome: Future strategies to identify the causative genes in individuals with DOORS syndrome but without TBC1D24 mutations could include consideration of oligogenic inheritance models, analysis of output for multiple different genes in the same pathway, an increase in enrolment and number of exomes or depth of exome sequencing, whole-genome sequencing, and analysis of exome data for copy-number variants.