Long-term response to deep brain stimulation of the globus pallidus internus in a patient of African origin with a homozygous DYT-AOPEP variant

Introduction: Zech-Boesch syndrome (DYT31 or DYT-AOPEP) is a rare autosomal recessive form of dystonia caused by bi-allelic loss-of-function variants in the AOPEP gene. It typically presents as early-onset, progressive, and frequently drug-resistant dystonia. Although Deep Brain Stimulation (DBS) of the Globus Pallidus internus (GPi) has demonstrated encouraging outcomes in other monogenic dystonias, evidence in DYT-AOPEP remains limited. Methods: We report the case of a patient with DYT-AOPEP, providing detailed clinical, genetic, and therapeutic characterization, along with long-term follow-up after DBS implant. Results: A 38-year-old Moroccan man developed dystonia at age 12, initially involving the right lower limb and subsequently generalizing, with prominent cranio-cervical, axial, and appendicular involvement, as well as tremor and choreiform features. Pharmacological treatments proved ineffective, whereas bilateral GPi-DBS, performed at age 21, resulted in sustained motor improvement. Thirteen years later, a sudden clinical worsening due to device malfunction necessitated revision of the neurostimulation system. Following DBS replacement and reprogramming, the patient achieved renewed marked clinical improvement over a two-year follow-up period, with a 41.7% reduction in the Burke–Fahn–Marsden Dystonia Rating Scale motor score (BFMDRS-M), from 48 to 28. The most notable benefits were observed in limb and trunk dystonia; tremor resolved completely, and gait and functional autonomy improved. Genetic analysis identified a rare homozygous nonsense variant in AOPEP (c.617dup p.Tyr206∗). Conclusions: This case broadens the phenotypic spectrum of DYT-AOPEP and represents the first genetically confirmed patient of African origin. It also provides the longest reported follow-up of GPi-DBS, supporting its sustained long-term efficacy in AOPEP-related dystonia.