Objective: The phenotypic spectrum in dystonic syndromes in childhood is wide. Mutations in KMT2B gene were first described in 2016 and it means mutations in the Histone-lysine-N-methyltransferase-2B gene, it occurs in heterozygous state (autossomal dominant).

Background: The majority of patients had generalized dystonia and it shows first symptoms at the age of 4 to 9 years-old. It’s a complex type of dystonia and there are other features described besides dyskinetic movements, such as dysmorphic features, cognitive impairment, development delay and short stature were also reported. Some reports of patients with DYT-KMT2B treated with Deep Brain stimulation (DBS) have been published. Early age of dystonia onset, short mean time to generalization and risk of status dystonicus should be considered for surgical management.

Method: A child with clinical history at the beggining of focal dystonia and progression to generalized dystonia  was examined in a movement disorder and neurogenetics reference center.

Results: A 9-year-old girl with an uneventful pregnancy and birth, parents were non-consanguineous, no history of neurologic disorders at her family. Her development was normal and at the age of 5 years-old she developed involuntary distonic movements on her left foot. It progress to the point of generalised dystonia at the age of 8 years-old. She also had swallowing difficulties and dysarthric speech. Brain MRI was unremarkable. Whole exome identified a pathogenic variant in gene KMT2B. Treatment with trihexyphenidyl, baclofen and botulinum toxin was introduced but with no improvement. The preoperative BFMDRS-M was 77. The patient was submitted to bilateral placement of globus pallidus internus deep brain stimulation (GPi-DBS). She had a pronounced improvement, BFMDRS-M after 6 months of DBS is 25,5.

Conclusion: Our case is illustrative to endorse GPi-DBS as an efficient therapeutic option for early-onset dystonia. Especially for improving limb dystonia and regaining independent mobility. Our patient had a great improvement with stimulation, 65% of improvement  on dystonic movement on the BFMDRS-M.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/dyt-kmt2b-generalized-dystonia-managed-with-gpi-dbs/