Mutations, Genes, and Phenotypes Related to Movement Disorders and Ataxias

Abstract

Our clinical series comprises 124 patients with movement disorders (MDs) and/or ataxia with cerebellar atrophy (CA), many of them showing signs of neurodegeneration with brain iron accumulation (NBIA). Ten NBIA genes are accepted, although isolated cases compatible with abnormal brain iron deposits are known. The patients were evaluated using standardised clinical assessments of ataxia and MDs. First, NBIA genes were analysed by Sanger sequencing and 59 patients achieved a diagnosis, including the detection of the founder mutation PANK2 p.T528M in Romani people. Then, we used a custom panel MovDisord and/or exome sequencing; 29 cases were solved with a great genetic heterogeneity (34 different mutations in 23 genes). Three patients presented brain iron deposits with Fe-sensitive MRI sequences and mutations in <i>FBXO7</i>, <i>GLB1</i>, and <i>KIF1A</i>, suggesting an NBIA-like phenotype. Eleven patients showed very early-onset ataxia and CA with cortical hyperintensities caused by mutations in <i>ITPR1</i>, <i>KIF1A</i>, <i>SPTBN2</i>, <i>PLA2G6</i>, PMPCA, and <i>PRDX3</i>. The novel variants were investigated by structural modelling, luciferase analysis, transcript/minigenes studies, or immunofluorescence assays. Our findings expand the phenotypes and the genetics of MDs and ataxias with early-onset CA and cortical hyperintensities and highlight that the abnormal brain iron accumulation or early cerebellar gliosis may resembling an NBIA phenotype.