A Patient with Corticobasal Syndrome and Progressive Non-Fluent Aphasia (CBS-PNFA), with Variants in , , , and Genes

Our aim was to analyze the phenotypic-genetic correlations in a patient diagnosed with early onset corticobasal syndrome with progressive non-fluent aphasia (CBS-PNFA), characterized by predominant apraxia of speech, accompanied by prominent right-sided upper-limb limb-kinetic apraxia, alien limb phenomenon, synkinesis, myoclonus, mild cortical sensory loss, and right-sided hemispatial neglect. Whole-exome sequencing (WES) identified rare single heterozygous variants in (c.3207C>A), (c.352G>A), (c.2385_2387delAAA), and (c.1762G>A) genes. The functional analysis revealed that the deletion in the gene changed the splicing pattern, which was accompanied by lower mRNA levels in the patient's fibroblasts, suggesting loss-of-function as the underlying mechanism. In addition, the patient's fibroblasts demonstrated altered mitochondrial architecture with decreased connectivity, compared to the control individuals. This is the first association of the CBS-PNFA phenotype with the most common pathogenic variant p.H1069Q, previously linked to Wilson's disease, and early onset Parkinson's disease. This study expands the complex clinical spectrum related to variants in well-known disease genes, such as , , , and , corroborating the hypothesis of oligogenic inheritance. To date, the gene has been linked exclusively to neurodevelopmental speech disorders, while our study highlights its possible relevance for adult-onset progressive apraxia of speech, which guarantees further study.