Familial Dystonia Due to Homozygous TPI1 c.718G>A (p.Glu240Lys): A Three-Sibling Case Series Including Two Treated with Deep Brain Stimulation of the Globus Pallidus Internus.

Triosephosphate isomerase (TPI) deficiency is a rare autosomal recessive disorder caused by mutations in the TPI1 gene, typically presenting with anemia, infections, and neurological decline. We report three siblings with a homozygous c.718G>A (p.Glu240Lys) variant presenting predominantly with dystonia. Clinical and genetic evaluations were performed in three affected siblings from a consanguineous Turkish family. Neurological examinations, imaging, and surgical outcomes were reviewed. All three siblings exhibited truncal and axial dystonia with orthopedic deformities but without anemia or cardiac involvement. Cognitive functions were preserved. Two underwent bilateral deep brain stimulation of the globus pallidus internus (GPi-DBS), resulting in partial yet clinically meaningful improvement in posture and gait. The third sibling received orthopedic interventions. Notably, one homozygous sibling remained asymptomatic, highlighting incomplete penetrance. This is the first genetically confirmed report of TPI1 -associated dystonia treated with GPi-DBS. Our findings expand the clinical spectrum of TPI deficiency, showing a neurologically predominant phenotype without hematologic manifestations. The observed variability suggests the role of modifier factors, and GPi-DBS may provide symptomatic benefit in severe cases.