Objective: To provide a description of a patient with rare DYT23 dystonia.

Background: DYT23 type dystonia is characterized by adult-onset, focal cervical dystonia typically manifesting with torticollis and occasionally accompanied by mild head tremor and essential-type limb tremor [1]. It is due to an autosomal dominant mutation in the CACN1B gene coding for a voltage gated calcium channel. The prevalence of DYT23 dystonia is unknown.

Method: Clinical description and laboratory testing.

Results: This 54-year-old patient complained of turning the head to the left, moderate to severe muscle pain and spasms in the muscles of the arms, abdomen and back, tremor of the arms and head, unsteadiness when walking, involuntary movements in the legs, difficulties with self-care and depression. Tremor of hands began about 40 years ago, with head turning for 5 years. He was started on 500 mg of levodopa per day and said that his symptoms decreased by 50%. He discontinued levodopa due to “dizziness and increased BP”. He was also tried on Baclofen 30 mg per day, Amantadine 200 mg per day, Pramipexole 1.5 mg per day, and Pregabalin 75 mg per night with no benefit. Currently, he started taking Trihexyphenidyl. Low doses of alcohol reduce tremor.

PMH: hepatic steatosis, chronic pancreatitis, angina pectoris.

Family history: his mother had hands tremor. No history of dystonia.

On examination: cranial nerves (including eye movements, speech and swallowing), muscle power, coordination and postural stability were normal. He had pronounced dystonic torticollis with head turned to the left with moderate “yes-yes” head tremor when the head was turned straight and “no-no” head tremor when the head turned to the left. There was moderate kinetic and postural tremor of both arms. He had moderate bradykinesia in the right arm and mild bradykinesia in other limbs. Muscle tone was moderately increased in the left arm and mildly increased in the other limbs. His walking was mildly slow, but arm swing was normal. No involuntary movements in the legs were seen during examination.

Investigation: Research exome sequencing showed a rare splicing heterozygous variant in CACNA1B (ENST00000277549) c.4949+6T>G. The gnomAD allele frequency of the variant is 0.00003447.

Conclusion: This case demonstrates the typical clinical picture and disease course in a 54-year-old patient with a rare splicing heterozygous variant in CACNA1B associated with DYT23. This was the first diagnosed DYT23 case in Ukraine.

References: 1. Adult-onset Cervical Dystonia, Dyt23 Type: website. URL: https://www.mendelian.co/diseases/dystonia-23-dyt23 (date of issue: 02/28/2025).

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MDS Abstracts - https://www.mdsabstracts.org/abstract/rare-dyt23-dystonia-first-diagnosed-case-in-ukraine/