TCF20 is a gene that encodes a transcriptional co-regulator, a protein that does not switch genes on or off by itself but modulates the activity of other gene-regulating machinery. During brain development, TCF20 helps orchestrate neurogenesis and the construction of dendrites and synapses, the branching connections through which neurons communicate. When one copy of the gene is disrupted, the result is typically TAND, a neurodevelopmental condition marked by developmental delay, intellectual disability, and behavioral abnormalities, sometimes accompanied by autism spectrum traits, attention deficits, low muscle tone, structural brain anomalies, and subtle facial dysmorphism. Motor symptoms such as unsteady gait, tremor, or coordination difficulties have been described, but dystonia has only recently begun to surface in the literature, and only in a handful of patients.

The patient in this report first came to medical attention with a story that unfolded over two decades. Her parents were not related, and no one in the family had similar problems. From early childhood, her speech was unclear, a feature that became more noticeable around preschool age. At eight years old, her right upper limb began to adopt abnormal postures, with semiflexion at the wrist and elbow, and she occasionally dragged her right foot while walking. Neurocognitive evaluation prompted by learning difficulties confirmed mild intellectual disability. At nine, similar symptoms emerged on the left side and progressed. By fifteen, she needed walking support and had developed cervical dystonia. At seventeen, contractions of her jaw impaired chewing of solid foods. From nineteen onward, her speech deteriorated until it became incomprehensible.

Neurological examination painted a detailed picture of a nervous system under widespread stress. She had marked dysarthria, hypophonia, diminished palatal reflexes, and restricted tongue movement, while eye movements remained normal. Bradykinesia and reduced facial expression were evident. Muscle tone testing revealed spasticity in the lower limbs and cogwheel rigidity in the upper limbs, particularly at the right wrist. The dystonia itself predominated in the cervical region, with anterocollis and right-sided laterocollis, along with truncal dystonia pulling her torso to the right. Jaw-closing dystonia was clear, and milder dystonic contractions, mainly of the flexors, appeared in the extremities. She also had a bilateral, left-predominant rest and postural tremor accompanied by titubation, brisk deep tendon reflexes, bilateral Achilles clonus, and spontaneous dorsiflexion of both great toes.

Cognitive testing showed preserved basic attention but marked deficits in sustained and executive attention and working memory, suggesting frontal dysfunction. Memory impairment appeared secondary to attentional deficits, with encoding preserved. Visual perception of static objects was severely impaired, pointing to dysfunction in the ventral stream, with right occipitotemporal predominance. Naming and spatial-temporal orientation were preserved, and her Mini-Mental State Examination score was 23 out of 30. Routine laboratory tests, cerebrospinal fluid analysis, electroencephalography, and electromyography were unremarkable. Fundoscopy and optical coherence tomography were normal.

Brain imaging offered a tantalizing clue. On 3-Tesla MRI, the globus pallidus appeared relatively hypointense bilaterally on T2-weighted and susceptibility-weighted imaging, raising the possibility of basal ganglia iron accumulation. To investigate further, the team performed quantitative susceptibility mapping, or QSM, a technique that measures magnetic susceptibility in tissue with far greater precision than conventional sequences, and volumetry of the deep gray matter nuclei. Using a cloud-based multi-atlas automated segmentation platform, they compared the patient with five age- and sex-matched controls. In the globus pallidus, magnetic susceptibility values were numerically higher bilaterally, particularly in the external segment, and volumes were lower than in controls. However, the single-patient design and variability among controls preclude formal statistical inference, so these exploratory findings cannot confirm or exclude a neurodegeneration-with-brain-iron-accumulation mechanism.

Genetic analysis provided the answer. Whole genome sequencing on the Illumina NovaSeq platform, analyzed with a pipeline that prioritized high- and moderate-impact protein-altering variants and focused on genes annotated to the HPO term Dystonia, identified a heterozygous TCF20 variant: c.932_933del, p.Gln311ArgfsTer22. Sanger sequencing showed the variant was absent from both parents, consistent with a de novo event. It was also absent from population databases including gnomAD and the RGC Million Exome Variant Browser, though it has been reported in ClinVar. The variant introduces a premature stop codon in exon 2 of TCF20, the first coding exon and an unusually large one spanning 5691 base pairs. It is predicted to cause loss of function, a known pathogenic mechanism in TAND, and is classified as pathogenic under ACMG criteria.

Treatment proved stubbornly difficult. A three-month levodopa trial, gradually escalated from 62.5 mg/day to a maximum of 250 mg/day, provided no clear benefit. Trihexyphenidyl, titrated to 18 mg/day, also failed to produce a satisfactory response. She is currently managed with periodic botulinum toxin injections, which provide partial relief of cervical and jaw-closing dystonia. The refractory nature of her symptoms underscores how little is known about the best therapeutic approach when dystonia dominates the TAND phenotype.

The case gains additional weight from a growing body of literature linking TCF20 loss-of-function variants to hyperkinetic movement disorders. Svorenova and colleagues reported two patients with previously unrecognized dystonia, one with a progressive spastic-ataxic-dystonic syndrome and another with childhood-onset toe-walking followed by generalized dystonia. Prasun and colleagues described an adolescent initially diagnosed with dystonic cerebral palsy who was later found to carry a de novo TCF20 loss-of-function variant. Magistrelli and colleagues reported a 70-year-old man who developed craniocervical dystonia and upper limb myoclonus in midlife. Collectively, these observations suggest that dystonia, whether progressive, fluctuating, or late-onset, represents a diagnostically important yet previously underestimated manifestation of TAND.

At the molecular level, the picture is becoming clearer. A recent study demonstrated a direct interaction between TCF20 and MeCP2, the protein implicated in Rett syndrome. Both proteins are highly co-expressed in neurons and regulate neuronal gene expression, a molecular link that may explain overlapping neurodevelopmental features in TCF20- and MECP2-related disorders, including the frequent association with autism spectrum disorder. Motor disturbances reported in Rett syndrome, such as tremor and ataxia, have also been described in TAND. The same TCF20 variant identified in this patient has previously been reported in two unrelated female patients, one identified through clinician questionnaires in which dystonia was not described and another through systematic reanalysis within Solve-RD, a large European rare disease reanalysis initiative, in which generalized dystonia was noted without detailed motor characterization. Shared features across reports include dysarthria, tremor, ataxia, and intellectual disability.

The study is limited by its single-case design, the small control sample, and the lack of functional validation. The QSM findings remain exploratory and were not intended for definitive patient-control comparisons. Nevertheless, the overall phenotype raises the possibility of a link between TCF20 dysfunction, globus pallidus alterations, and dystonia pathophysiology, warranting further investigation in larger cohorts. For clinicians, the message is straightforward: detailed clinical phenotyping can guide genetic diagnosis, and TCF20 deserves a place in relevant gene panels when dystonia appears alongside neurodevelopmental features. For patients and families, the case offers something rarer than a treatment: a name for what is happening, and a growing community of researchers paying attention.

Subject of Research: Generalized Dystonia With Cervical Predominance in a Patient With a De Novo TCF20 Variant

Article Title: Generalized Dystonia With Cervical Predominance in a Patient With a De Novo TCF20 Variant

Article References: Kilic, M., Dusek, P., Kamaci, I., Gulmez, B., Cakmakli, G. Y., Tan, E., Ugur Iseri, S., & Yapici, Z. (2026). Generalized Dystonia With Cervical Predominance in a Patient With a De Novo TCF20 Variant. Annals of Clinical and Translational Neurology, Article acn3.70534. https://doi.org/10.1002/acn3.70534

Image Credits: AI Generated

DOI: 10.1002/acn3.70534

Keywords: Generalized, Dystonia, Cervical, Predominance, Patient, Novo, TCF20, Variant, scientific research