© 2021 S. Karger AG, Basel.In this study, we report the first known Turkish case of a novel nonsense mutation c.2453dupT (p.M818fs∗28) in the KMT2B (NM_014727.2) gene diagnosed in a male patient with KMT2B-related dystonia (DYT-KMT2B, DYT-28, Dystonia∗-28), which is a complex, childhood-onset, progressive, hereditary dystonia. The patient, who is followed up from 9 to 13 years of age, had dysmorphic features, developmental delay, short stature, and microcephaly, in addition to focal dystonia and hemichorea (in the right and left lower extremities). Generalized dystonia involving bulbar and cervical muscles, in addition to dystonic cramps, myoclonus, and hemiballismus, were also observed during the course of the follow-up. While he was able to perform basic functions like eating, climbing stairs, walking, and writing with the aid of levodopa and trihexyphenidyl treatment, his clinical status gradually deteriorated secondary to progressive generalized dystonia in the 4-year follow-up. Deep brain stimulation has been shown to be effective in several patients which could be the next preferred treatment for the patient.