DYT-TUBB4A (DYT4 Dystonia): New Clinical and Genetic Observations.

OBJECTIVE:To report 4 novel TUBB4A mutations leading to laryngeal and cervical dystonia with frequent generalization. METHODS:We screened 4 families including a total of 11 definitely affected members with a clinical picture resembling the original description. RESULTS:Four novel variants in the TUBB4A gene have been identified: D295N, R46M, Q424H, and R121W. In silico modeling showed that all variants have characteristics similar to R2G. The variants segregate with the disease in 3 of the families with evidence of incomplete penetrance in 2 of them. All 4 variants would be classified as likely pathogenic. The clinical picture particularly included laryngeal dystonia (often the site of onset), associated with cervical and upper limb dystonia and frequent generalization. Laryngeal dystonia was extremely prevalent (>90%) both in the original cases and in this case series. The hobby horse gait was evident in only 1 patient in this case series. CONCLUSIONS:Our interpretation is that laryngeal involvement is a hallmark feature of DYT-TUBB4A. Nevertheless, TUBB4A mutations remain an exceedingly rare cause of laryngeal or other isolated dystonia.