ANK3 encodes ankyrin-G, a key scaffolding protein essential for neuronal function. While both monoallelic and biallelic ANK3 variants have been linked to neurodevelopmental disorders (NDDs), existing evidence for their pathogenicity and clinical correlation remains limited and heterogeneous. To delineate the clinical features associated with biallelic ANK3 predicted loss-of-function (pLOF) variants. We employed exome sequencing, Sanger validation, detailed clinical phenotyping, and extensive international data sharing to identify patients with biallelic ANK3 variants. We describe five individuals from three unrelated consanguineous families with segregating homozygous ANK3 pLOF variants. These patients presented with a relatively consistent phenotype comprising developmental delay, intellectual disability, hypotonia, variable epilepsy, and cerebellar signs including ataxia, tremor, and dysarthria. Among the three patients for whom brain magnetic resonance imaging was available, cerebellar atrophy was observed, predominantly affecting the superior vermis and cerebellar hemispheres. These clinical findings align with murine models lacking the cerebellar ankyrin-G isoform, which similarly exhibit ataxic features and high cerebellar ANK3 expression. Our findings support a recognizable NDD with non-progressive cerebellar ataxia linked to biallelic ANK3 pLOF variants. © 2025 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

L-2-hydroxyglutaric aciduria (L-2-HGA, #236,792) is an autosomal recessive neurodegenerative disorder caused by the deficiency of L-2-hydroxyglutarate dehydrogenase, a flavin adenine dinucleotide (FAD)-dependent enzyme, due to biallelic pathogenic variants in the L2HGDH gene. The present study described the patient with L2HGA presenting with a slight psychomotor delay, epilepsy from 5 years of age, non-progressive cerebellar ataxia, and mild to moderate intellectual disability during 10 years of follow-up. Two different heterozygous variants in the L2HGDH gene were identified in the patient: a known substitution c.829C > T(p.Arg277*) and a novel substitution c.1196 + 1G > A corresponding with significantly increased urinary L-2-hydroxyglutarate (L2HG) excretion. A 6-month period of treatment with riboflavin (100 mg/day) was implemented with no clinical nor biochemical effect.

Cerebellar ataxia, mental retardation, and dysequilibrium (CAMRQ) syndrome is a rare neurodevelopmental disorder characterized by non-progressive cerebellar ataxia, intellectual disability, and cerebellar atrophy. Despite its rarity, CAMRQ syndrome poses significant challenges due to its heterogeneous genetic etiology and complex clinical presentation. This study details the evolving clinical phenotype over 7 years in a male with CAMRQ4 syndrome caused by an in-frame deletion variant in ATP8A2 gene. A detailed clinical evaluation was performed, accompanied by tests and imaging studies. Clinical and genetic investigations, including segregation analysis, were carried out to confirm the pathogenicity of the identified variant. The evolving clinical phenotype of the patient, including developmental delay, cerebellar ataxia, and hand-foot crawling, was thoroughly investigated. A 10-year-old male patient with CAMRQ syndrome exhibited typical clinical manifestations including impaired motor coordination, cognitive impairment, and balance disturbances. Genetic analysis revealed a homozygous in-frame deletion variant (c.1286_1288delAGA) in the ATP8A2 gene, implicating ATP8A2 in the pathogenesis of CAMRQ syndrome. This variant was predicted to be likely pathogenic and deleterious, in accordance with its segregation in affected family members. Our findings expand the mutational spectrum of ATP8A2-associated CAMRQ syndrome and underscore the importance of comprehensive genetic testing in diagnosing rare neurological disorders. The identification of an in-frame deletion variant in the ATP8A2 gene enhances our understanding of CAMRQ syndrome and highlights the phenotypic variability of the disorder. Our study contributes to the elucidation of CAMRQ syndrome by identifying a novel genetic variant and elucidating its clinical and genetic implications. Further research is warranted to advance our understanding of CAMRQ syndrome and to improve patient care and management strategies.

Poretti-Boltshauser Syndrome (PBS) is a rare neuro-ophthalmological disorder with autosomal recessive inheritance. It is characterized by non-progressive cerebellar ataxia, delay in neuropsychomotor development, intellectual disability, and vision abnormalities. PBS is caused by mutations in the LAMA1 gene, resulting in cerebellar abnormalities, including cerebellar cysts in most cases. We present two siblings with LAMA1 mutations and distinct phenotypic presentation, with one of them showing no evidence of cerebellar cysts on magnetic resonance imaging (MRI). This study highlights intrafamilial variability in patients with Poretti-Boltshauser Syndrome (PBS). Patient 1 exhibits more pronounced cerebellar dysplasia (with cysts) and oculomotor apraxia, while Patient 2 shows milder cerebellar dysplasia (without cysts) and a macular hole. These findings underscore the importance of comprehensive evaluation and genetic testing for accurate diagnosis and management of PBS.

Pathogenic variants in B-cell receptor-associated protein (BCAP31) are associated with X-linked, deafness, dystonia and cerebral hypomyelination (DDCH) syndrome. DDCH is congenital and non-progressive, featuring severe intellectual disability (ID), variable dysmorphism, and sometimes associated with shortened survival. BCAP31 encodes one of the most abundant chaperones, with several functions including acting as a negative regulator of endoplasmic reticulum (ER) calcium ion (Ca2+) concentration. Here, we characterize an X-linked syndrome, its underlying genotype, and a functional evaluation of the identified candidate genetic variant. Evaluation of motor features, neuroimaging studies, neurophysiological, and cognitive tests. Whole exome sequencing (WES) was applied, a plasmid encoding BCAP31 with and without a candidate variant was transfected into SH-SY5Y cells to assess subcellular location and to measure Ca2+ levels in the cytoplasm. Adult-onset ataxia, cognitive impairment, and hearing loss leading to deafness are the predominant features. Reduced penetrance, slow progression with preserved ability to walk in advance age, and universal cerebellar atrophy are other features for this syndrome. This condition is associated with the new variant c.22G>A (V8I) in BCAP31 at Xq28. The subcellular location of the V8I BCAP31 protein was not altered but caused significant elevation of cytosolic Ca2+. Our findings expand the spectrum of variants in BCAP31 from neurodevelopmental syndromes to include a progressive neurodegenerative disease with variable expressivity. This is the first time ataxia is described in association with a BCAP31 variant and functional evidence of pathogenicity is provided. Additional BCAP31 cases featuring ataxia are needed to establish an association. © 2025 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.