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A Case of Childhood Onset Dystonia Due to KMT2B Gene Mutation

Objectives: Dystonia 28 is an autosomal dominant inherited disorder characterized by the onset of progressive dystonia in the first decade of life. This text was aimed to emphasize the KMT2B gene mutation, which is one of the genetic causes of dystonia.

Case: A nine-year-old male patient presented with inward walking in his left foot. The patient, who could walk and run until the age of eight, had complaints of inward walking in the left foot, inability to run, and pain in the left foot for the last year. It was learned that similar gait and pain were also present in the father who passed away. In the patient's neurological examination, bilateral lower extremities' deep tendon reflexes were hyperactive. Spasticity was present in the bilateral lower extremities, especially on the left. The patient had a dystonic gait and had pain with walking. The patient's cranial and spinal magnetic resonance imaging findings were normal. In the whole-exome sequence analysis. c.3646_3653del heterogeneous pathogenic mutation was detected in the KMT2B gene. This variant has not been reported before, but evaluations in databases have classified the variant as likely pathogenic. This mutation, which was confirmed by Sanger sequence analysis, was not detected in the mother, and samples could not be taken from the father due to death. The patient was diagnosed with Dystonia 28.

Conclusion: Hereditary dystonia should be considered in the differential diagnosis of patients presenting with late-onset gait disturbance and spasticity.
Keywords: "child, dystonia, gait disturbance, spasticity"