Dentatorubral-pallidoluysian atrophy (DRPLA) is a rare autosomal dominant neurodegenerative disease caused by a CAG repeat expansion in the ATN1 gene. The juvenile onset type often presents with epilepsy, including progressive myoclonic epilepsy (PME). However, evidence on epilepsy in DRPLA remains limited. This systematic review and meta-analysis aimed to summarize clinical characteristics of DRPLA-related epilepsy. We systematically searched MEDLINE (PubMed), CENTRAL, Embase, Ichushi, and ClinicalTrials.gov for studies on DRPLA-related epilepsy, following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The review protocol was registered with the Open Science Framework. Any study design reporting at least one case of DRPLA-related epilepsy was eligible, including case reports, case series, cohort studies, and clinical trials. Eligible studies underwent screening and full-text assessment, followed by inclusion in descriptive and meta-analytic syntheses. Meta-analyses included only studies reporting ≥5 DRPLA patients. A total of 181 studies encompassing 1191 patients met the eligibility criteria. DRPLA patients with epilepsy had a younger onset age (16.9 [95% confidence interval (CI) = 13.76-20.76] vs. 45.5 years [95% CI = 42.77-48.47]) and more CAG repeats (66.7 [95% CI = 63.63-69.84] vs. 59.2 [95% CI = 55.67-62.92]) than those without epilepsy. DRPLA patients with epilepsy showed a higher likelihood of paternal versus maternal inheritance (odds ratio = 2.47 [95% CI = .97-6.27]). Focal seizures were frequently observed (40.0%-76.5%) alongside myoclonic and generalized tonic-clonic seizures. Electroencephalographic findings included slow bursts (38.0%), photoparoxysmal responses (36.6%), and interictal epileptiform discharges (77.5%). Giant somatosensory-evoked potentials, typically seen in PME, were observed in only two patients and absent in 27. Among antiseizure medications, perampanel and levetiracetam were more frequently reported as effective than sodium channel blockers. This review synthesizes fragmented evidence on DRPLA-related epilepsy and highlights key clinical and electrophysiological patterns. Despite limitations from small-scale studies, these findings support more informed clinical care and underscore the need for larger cohort studies.

Several genetic diseases affecting the human nervous system are incurable and insufficiently understood. Among them, nine rare diseases form the polyglutamine (polyQ) family: Huntington's disease (HD), spinocerebellar ataxia types 1, 2, 3, 6, 7, and 17, dentatorubral pallidoluysian atrophy, and spinal and bulbar muscular atrophy. In most patients, these diseases progress over decades to cause severe movement incoordination and neurodegeneration. Although their inherited genes with tandem-repeat elongations and the encoded polyQ-containing proteins have been extensively studied, the neuronal-type-specific pathologies and their long pre-symptomatic latency await further investigations. However, recent advances in detecting the single-nucleus transcriptome, alongside the length of tandem repeats in HD post-mortem brains, have enabled the identification of very high CAG repeat sizes that trigger transcriptional dysregulation and cell death in specific projection neurons. One challenge is to better understand the complexity of movement coordination circuits, including the basal ganglia and cerebellum neurons, which are most vulnerable to the high CAG expansion in each disease. Another challenge is to detect dynamic changes in CAG repeat length and their effects in vulnerable neurons at single-cell resolution. This will offer a platform for identifying pathological events in vulnerable long projection neurons and developing targeted therapies for all tandem-repeat expansions affecting the CNS projection neurons.

Neuronal ceroid lipofuscinosis (NCL) is a heterogeneous group of lysosomal disorders characterized by progressive psychomotor regression, visual impairment, and intractable seizures. Genetically, NCL type 3 (CLN3) is associated with variants in the gene encoding a lysosomal transmembrane protein. To date, few Japanese patients with CLN3 have been reported. Thus, their neurodevelopmental and clinical features remain unclear. Here, we report the clinical course of a genetically confirmed Japanese patient with CLN3. A 17-year-old Japanese boy was diagnosed with retinitis pigmentosa at age 7. Visual impairment progressed over a 10-year follow-up period. Generalized tonic-clonic seizures also began at age 7. Developmental regression was recognized at age 13, with an accelerated decline in motor and communication skills following a COVID-19 infection at age 17. Tube feeding and gastrostomy were initiated for dysphagia and recurrent respiratory infections. Serial MRI revealed progressive cerebral and cerebellar atrophy. Lymphopenia (351-1467/μL) was present from age 9; peripheral blood smear revealed vacuolated lymphocytes. Exome sequencing identified a heterozygous CLN3 variant, NM_001042432.2:c.295-2A > C. SpliceAI suggested exon 6 skipping and/or an 80-bp deletion, leading to nonsense-mediated mRNA decay. Manual inspection using Integrated Genomic Viewer revealed a second variant (c.178_180delinsACATCCTTAGCCACAAGAG) missed initially. Trio Sanger sequencing confirmed compound heterozygosity: NM_001042432.2:c.[295-2A > C]; [178_180delinsACATCCTTAGCCACAAGAG] p.[?]; [His60Thrfs∗10]. A review of 430 genetically confirmed CLN3 patients (1989-2025) identified no hematologic abnormalities. This Japanese CLN3 patient developed visual impairment 7-8 years before systemic deterioration. Retinal degeneration, together with vacuolated peripheral lymphocytes, may provide early diagnostic clues for CLN3 in Japanese patients.

We report two cases of dual genetic diagnoses involving Lafora disease (LD) and co-occurring neurodevelopmental disorders caused by pathogenic variants in TRIO and SHANK3, respectively. LD is an ultra-rare, autosomal recessive, severe form of progressive myoclonus epilepsy affecting previously healthy children or adolescents. In both patients, the presence of developmental delay, intellectual disability, and behavioral abnormalities was consistent with a primary genetic disorder-TRIO-related neurodevelopmental disorder in one, and Phelan-McDermid syndrome in the other. However, the onset of epilepsy with atypical features, coupled with progressive neurological decline in one patient and a positive family history of LD in the other, prompted the additional diagnosis of LD. These cases illustrate how overlapping clinical presentations can obscure the presence of concomitant genetic conditions, potentially delaying diagnosis and appropriate management. Our findings underscore the importance of considering dual diagnoses and show that phenotypical variability in ultra-rare disorders such as LD may be influenced by concurrent genetic conditions. PLAIN LANGUAGE SUMMARY: This report describes two patients who have both Lafora disease, an ultra-rare, progressive type of epilepsy, and other rare genetic disorders that affect development and behavior. In one case, the patient showed a progressive and unusual neurological deterioration, while the other had atypical epileptic seizures and a family history of Lafora disease. These cases highlight how different genetic conditions can share similar symptoms, making it difficult to identify all the issues a patient may have. Understanding these overlaps is important for proper diagnosis and treatment.

Next-generation sequencing (NGS) has expedited the diagnostic process and unearthed many rare disorders in leukodystrophy (LD) and genetic leukoencephalopathy (gLE). Despite the progress in genomics, there is a paucity of data on the distribution of genetic white matter disorders (WMDs) and the diagnostic utility of NGS-based assays in a clinical setting. This study was initiated to explore the clinical, radiologic, and genetic spectrum of LD and gLE in the Indian population and also to estimate the diagnostic yield of clinical exome sequencing (CES). This is a retrospective descriptive analysis of patients with a diagnosis of genetic WMDs from a single tertiary referral center who had CES performed as part of the diagnostic evaluation between January 2016 and December 2021. The demographic, clinical, radiologic, and genetic data were collected. The variants were classified using the American College of Medical Genetics and Genomics criteria. Pathogenic and likely pathogenic variants were included in the calculation of the diagnostic yield. In the study period, 138 patients were clinically diagnosed with either LD or gLE, of which 86 patients underwent CES. Pathogenic variants, likely pathogenic variants, and variants of uncertain significance with phenotype match were seen in 40 (41.8%), 13 (29.1%), and 15 (15.2%) patients, respectively. The mean age at onset in these 68 patients was 6.35 years (range 1 month-39 years), and 38 (55.9%) were male. LDs and gLE were diagnosed in 31 and 37 patients, respectively. 56 patients (71.8%) had autosomal recessive inheritance. The common clinical presentations were developmental delay (23.5%), psychomotor regression (20.6%), progressive myoclonic epilepsy syndrome (19.1%), and spastic ataxia (14.7%). Myelin disorders (48.5%) and leuko-axonopathies (41.2%) were the commonest type of disorders. The most frequently identified genes were ARSA, CLN5, ABCD1, CLN6, TPP1, HEXA, and L2HGDH. The diagnostic yield of the study was 61.6% (53/86), which increased to 79.1% when VUS with phenotype match were included. This study demonstrated a high diagnostic yield from proband-only CES in the evaluation of genetic WMDs and should be considered as a first-line investigation for genetic diagnosis. This study provides Class IV evidence that proband-only clinical exome sequencing is a useful "first-line investigation" for patients with genetic white matter disorders.