Phenotype and genotype features of 11 children with dystonia 28 caused by KMT2B variants / 中华实用儿科临床杂志

ABSTRACT

Objective:To summarize the clinical characteristics of children with dystonia 28 (DYT28) caused by KMT2B gene variations so as to improve clinicians′ understanding of the disease. Methods:The clinical manifestations, treatment and gene variation data of 11 children with DYT28 caused by KMT2B gene variations were retrospectively collected and analyzed.The subjects were recruited from the Department of Neurology, Beijing Children′s Hospital, Capital Medical University from March 2018 to January 2021.The patients were followed up. Results:There were 8 males and 3 females.The age at onset was ranging from 1 month to 6 years without inducement.Eight cases were gene-ralized dystonia and 3 cases were multifocal dystonia.The initial symptoms of 7 cases were unilateral or bilateral lower limbs tiptoeing.Four cases presented dysarthria, retching or swallowing difficulties at onset.As the disease progressed, all the cases had laryngeal dystonia, 10 cases had lower limbs dystonia, and 8 cases had upper limbs dystonia.Six cases were complicated with other dyskinesia symptoms.Ten cases had varying degrees of short stature, microcephalus, micrognathia, musculoskeletal abnormalities, intellectual disability, endocrinopathies and sleep difficulties.The brain magnetic resonance imaging showed abnormal in only 1 case.Eleven KMT2B gene pathogenic variants were found, including 8 frameshift variants, 1 in-frame variant and 2 missense variants.Four variants were novel.Eleven cases were followed up at the age of 1 year and 7 months to 17 years and 9 months.One case wasn′t given therapy.The dystonia in 3 cases was mildly improved after medication.Dysfunction of urination and defecation was disappeared in 1 case after medication.The symptom of 6 cases had no improvement after drug therapy.Among the above 6 cases, 5 drug refractory cases had deep brain stimulation, and their dystonia symptoms are all obviously improved; 2 cases had normal control of urination and defecation after deep brain stimulation.The motor scores in the Burke-Fahn-Marsden dystonia rating scale were improved by 55.8%-90.7%, and the disability scores were improved by 14.8%-69.6%. Conclusions:DYT28 caused by KMT2B gene variations is one of the most common and early-onset genetic dystonia in children.The dystonia symptom progresses from local parts to the whole body, prominently involving laryngeal muscles and lower limbs.Control of urination and defecation requires attention.Patients with mild dystonia symptoms can be effectively treated by drugs.However, patients with severe dystonia symptoms were drug refractory, and their dystonia symptoms can be effectively improved by deep brain stimulation.