Additionally, TUBB4A mutations are known to result in a broad phenotypic spectrum, ranging from primary dystonia (DYT4), isolated hypomyelination with spastic quadriplegia, and an infantile onset encephalopathy, suggesting multiple cell types may be involved.
Moreover, given its allelic association with leukoencephalopathy hypomyelination with atrophy of basal ganglia and cerebellum and protean clinical manifestations (chorea, ataxia, dysarthria, intellectual disability, dysmorphic facial features, and psychiatric disorders), DYT4 should not be categorized as a primary dystonia.
In just over a year, four new genes have been shown to cause primary dystonia (CIZ1, ANO3, TUBB4A and GNAL), PRRT2 has been identified as the cause of paroxysmal kinesigenic dystonia and other genes, such as SLC30A10 and ATP1A3, have been linked to more complicated forms of dystonia or new phenotypes.