Dystonia related to the KMT2B gene: case report

*Correspondence: [e-mail].

Abstract

Case Presentation: LEN, 4 years old, previously healthy, perinatal history without abnormalities, started with symptoms of encephalitis-typical behavioral and laboratory changes, started corticosteroid therapy and immunomodulation, with improvement of symptoms. At 5 years of age, the disease flared up and received pulsetherapy and human immunoglobulin, this time with little therapeutic response. Protocolly indicated to use of rituximab with improvement. It remained stable until age 7. After that age, the condition began to regress, with dystonia of the face and limbs, making it impossible to walk, change in behavior-aggressiveness. Complementary and genetic investigations were carried out, the neuroimaging was normal, and the exome showed a condition associated with the KMT2B gene. The patient faces persistent facetrism dystonia and dysphagia, using anticholinergics, benzodiazepines, atypical antipsychotics and cannabidiol with partial control of symptoms.

Discussion: Dystonia is the most common hyperkinetic movement disorder in pediatrics, characterized by sustained or intermittent muscle contractions, causing abnormal and repetitive movements and postures. Dystonia related to the KMT2B gene is a complex movement disorder with onset in childhood whose prevalence is not established, so far it has been reported to occur in 39 individuals. Inherited in an autosomal dominant manner, the disease has a progressive course, evolving from focal dystonia of the lower limbs to generalized dystonia with cervical, cranial and laryngeal involvement. Regarding reported related psychiatric comorbidities, cognitive impairment with neurodevelopmental retraction, attention-deficit/hyperactivity disorder and obsessive-compulsive disorder were described. Although KMT2B-related disease is emerging as one of the most common causes of early-onset genetic dystonia, much remains to be understood about the disease as well as its pharmacological management, the use of high-dose anticholinergics in conjunction with benzodiazepines is described as an effective combination, still in discussion about the benefits in deep brain stimulation. Regarding the accurate investigative genetic examination, the complete exomic sequence is suggested as a first-line option in cases of complex or combined dystonia due to its good performance and effectiveness in detecting associated variants.

Final Comments: KMT2B gene mutation is an etiological entity of severe and early dystonia whose diagnosis requires genetic study and strategic treatment.

Publication History

Article published online:
12 May 2025