This syndrome is characterized by microcephaly, severe intellectual deficit, phalangeal anomalies (cutaneous syndactyly of the fingers, toe brachyclinodactyly and nail hypoplasia) and neurological manifestations (epilepsy, spastic/dystonic paraplegia and brisk reflexes).

Torsion dystonia-6 (DYT6) is an autosomal dominant movement disorder characterized by early involvement of craniofacial muscles with secondary generalization often involving the arms, and laryngeal dystonia that causes speech difficulties (review by Djarmati et al., 2009). Blanchard et al. (2011) provided a review of dystonia-6 and the THAP1 gene.

DYT-GNAL caused by a heterozygous GNAL pathogenic variant has been reported in more than 60 individuals to date. It is characterized by adult-onset isolated dystonia (i.e., no neurologic abnormalities other than tremor are evident on neurologic examination). The dystonia is most commonly focal and segmental, and rarely generalized. Dystonia is typically cervical in onset and commonly progresses to the cranial region (oromandibular/jaw, larynx, eyelids) and/or to one arm. Tremor reported in DYT-GNAL may be dystonic (i.e., occurring in a body part that shows at least minimal signs of dystonia) and may precede or follow the onset of dystonia. Intra- and interfamilial variability is considerable. DYT-GNAL caused by biallelic GNAL pathogenic variants, reported to date in two sibs from a consanguineous family, is characterized by mild intellectual disability and childhood-onset hypertonia that progresses to generalized dystonia.