We describe a 30-year-old woman with genetically confirmed Cri du Chat syndrome (CdCS) with cervical and right arm dystonia.

CdCS or 5p- syndrome, is a rare chromosomal disorder caused by a deletion on the short arm of chromosome 5. It is characterized by a high-pitched cry in infancy, microcephaly, intellectual disability, and distinct craniofacial features. While motor delays are common in childhood, persistent or emerging movement disorders in adulthood such as dystonia are rarely documented. Our patient (diagnosed previously by karyotype) developed right upper extremity posturing over the past three years, significantly impairing daily function. Examination revealed dystonic elbow extension and external rotation of the right arm, accompanied by cervical dystonia including retrocollis, right laterocollis, and left torticollis. She underwent chromosomal microarray analysis (CMA) testing and received botulinum toxin injections with symptomatic benefit.

CMA showed loss of 5p15.33p15.2 , and 6p25.1 (LYRM4 exons 1/2, FARS2 5' noncoding region). The affected region includes multiple genes implicated in neuronal development (e.g. SLC6A3, TPPP, CTNND2), cognitive and behavioural function (e.g., TERT, MED10). SLC6A3, which encodes a dopamine transporter, is a conditionally haplo-insufficient gene that has been previously associated with dystonia and parkinsonism phenotypes.

This case illustrates a rare presentation of segmental dystonia in an adult with Cri du Chat syndrome. While ADHD is frequently observed in individuals with Cri du Chat syndrome, reports of dystonia are rare. A potential explanation is that genes like SLC6A3 may exert dose-dependent effects, where partial loss of function can lead to variable phenotypic outcomes. This mechanism may have contributed to the development of isolated segmental dystonia in this patient.