Adult-Onset SCAR4 with a 30-Year Slowly Progressive Course: First Combined Assessment with FDG-PET and Brain Perfusion SPECT

Autosomal recessive spinocerebellar ataxia type 4 (SCAR4), caused by biallelic vacuolar protein-sorting 13D (VPS13D) variants, is a rare, clinically heterogeneous disorder. To describe an adult-onset SCAR4 case with a 30-year course and compare its features to those of published cases. We analyzed the clinical and imaging findings of a 58‑year‑old man and performed a literature review with pooled analysis of reported VPS13D/SCAR4 cases. The patient developed gait disturbance in his twenties, followed by progressive cerebellar and sensory ataxia, pyramidal signs, and peripheral neuropathy. MRI showed mild cerebellar atrophy. Fluorodeoxyglucose positron emission tomography and brain perfusion single-photon emission computed tomography revealed slightly reduced signals in the anterior cerebellum. Whole-exome sequencing revealed compound heterozygous VPS13D variants, including a pathogenic frameshift and a likely pathogenic missense variant. A literature review identified 47 cases. SCAR4 should be considered in sporadic adults with cerebellar ataxia, pyramidal signs, and peripheral neuropathy.