In addition to the higher rate of novel mutations of the BTK gene (42% in this study), approximately 10% of patients were CGS affecting the BTK and TIMM8A genes and presented with the DDON/MTS phenotype characterized by early-onset progressive post-lingual sensorineural deafness, gradual dystonia, and optic atrophy, which indeed required aggressive psychomotor re-education and physical therapy. Here, BTK is linked to hereditary optic atrophy.