Hereditary spastic paraplegia and extensive leukoencephalopathy: a case report of a unique phenotype associated with a GJB1/Cx32 p.Pro174Ser variant.

BACKGROUND: Pathogenic variants in Gap junction protein beta 1 (GJB1), which encodes Connexin 32, are known to cause X-linked Charcot-Marie-Tooth disease (CMTX), the second most common form of CMT. CMTX presents with the following five central nervous systems (CNS) phenotypes: subclinical electrophysiological abnormalities, mild fixed abnormalities on neurological examination and/or imaging, transient CNS dysfunction, cognitive impairment, and persistent CNS manifestations. CASE PRESENTATION: A 40-year-old Japanese male showed CNS symptoms, including nystagmus, prominent spastic paraplegia, and mild cerebellar ataxia, accompanied by subclinical peripheral neuropathy. Brain magnetic resonance imaging revealed hyperintensities in diffusion-weighted images of the white matter, particularly along the pyramidal tract, which had persisted since childhood. Nerve conduction assessment showed a mild decrease in motor conduction velocity, and auditory brainstem responses beyond wave II were absent. Peripheral and central conduction times in somatosensory evoked potentials elicited by stimulation of the median nerve were prolonged. Genetic analysis identified a hemizygous GJB1 variant, NM_000166.6:c.520C > T p.Pro174Ser. CONCLUSIONS: The patient in the case described here, with a GJB1 p.Pro174Ser variant, presented with a unique CNS-dominant phenotype, characterized by spastic paraplegia and persistent extensive leukoencephalopathy, rather than CMTX. Similar phenotypes have also been observed in patients with GJC2 and CLCN2 variants, likely because of the common function of these genes in regulating ion and water balance, which is essential for maintaining white matter function. CMTX should be considered within the spectrum of GJB1-related disorders, which can include patients with predominant CNS symptoms, some of which can potentially be classified as a new type of spastic paraplegia.

Complete nanopore repeat sequencing of SCA27B (GAA-FGF14 ataxia) in Japanese.

BACKGROUND: Although pure GAA expansion is considered pathogenic in SCA27B, non-GAA repeat motif is mostly mixed into longer repeat sequences. This study aimed to unravel the complete sequencing of FGF14 repeat expansion to elucidate its repeat motifs and pathogenicity. METHODS: We screened FGF14 repeat expansion in a Japanese cohort of 460 molecularly undiagnosed adult-onset cerebellar ataxia patients and 1022 controls, together with 92 non-Japanese controls, and performed nanopore sequencing of FGF14 repeat expansion. RESULTS: In the Japanese population, the GCA motif was predominantly observed as the non-GAA motif, whereas the GGA motif was frequently detected in non-Japanese controls. The 5'-common flanking variant was observed in all Japanese GAA repeat alleles within normal length, demonstrating its meiotic stability against repeat expansion. In both patients and controls, pure GAA repeat was up to 400 units in length, whereas non-pathogenic GAA-GCA repeat was larger, up to 900 units, but they evolved from different haplotypes, as rs534066520, located just upstream of the repeat sequence, completely discriminated them. Both (GAA)≥250 and (GAA)≥200 were enriched in patients, whereas (GAA-GCA)≥200 was similarly observed in patients and controls, suggesting the pathogenic threshold of (GAA)≥200 for cerebellar ataxia. We identified 14 patients with SCA27B (3.0%), but their single-nucleotide polymorphism genotype indicated different founder alleles between Japanese and Caucasians. The low prevalence of SCA27B in Japanese may be due to the lower allele frequency of (GAA)≥250 in the Japanese population than in Caucasians (0.15% vs 0.32%-1.26%). CONCLUSIONS: FGF14 repeat expansion has unique features of pathogenicity and allelic origin, as revealed by a single ethnic study.

RNA Foci in Two bi-Allelic RFC1 Expansion Carriers.

Cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) is a late-onset, autosomal recessive neurodegenerative disorder caused by biallelic AAGGG/ACAGG repeat expansion (AAGGG-exp/ACAGG-exp) in RFC1. The recent identification of patients with CANVAS exhibiting compound heterozygosity for AAGGG-exp and truncating variants supports the loss-of-function of RFC1 in CANVAS patients. We investigated the pathological changes in 2 autopsied patients with CANVAS harboring biallelic ACAGG-exp and AAGGG-exp. RNA fluorescence in situ hybridization of the 2 patients revealed CCTGT- and CCCTT-containing RNA foci, respectively, in neuronal nuclei of tissues with neuronal loss. Our findings suggest that RNA toxicity may be involved in the pathogenesis of CANVAS. ANN NEUROL 2024;95:607-613.

Rapid and comprehensive diagnostic method for repeat expansion diseases using nanopore sequencing.

We developed a diagnostic method for repeat expansion diseases using a long-read sequencer to improve currently available, low throughput diagnostic methods. We employed the real-time target enrichment system of the nanopore GridION sequencer using the adaptive sampling option, in which software-based target assignment is available without prior sample enrichment, and built an analysis pipeline that prioritized the disease-causing loci. Twenty-two patients with various neurological and neuromuscular diseases, including 12 with genetically diagnosed repeat expansion diseases and 10 manifesting cerebellar ataxia, but without genetic diagnosis, were analyzed. We first sequenced the 12 molecularly diagnosed patients and accurately confirmed expanded repeats in all with uniform depth of coverage across the loci. Next, we applied our method and a conventional method to 10 molecularly undiagnosed patients. Our method corrected inaccurate diagnoses of two patients by the conventional method. Our method is superior to conventional diagnostic methods in terms of speed, accuracy, and comprehensiveness.

Ocular flutter as the presenting manifestation of autoimmune glial fibrillary acidic protein astrocytopathy.

A 39-year-old man exhibited ocular flutter and cerebellar ataxia following a subacute disturbance of consciousness and partial seizure. He was diagnosed with autoimmune glial fibrillary acidic protein (GFAP) astrocytopathy by tissue- and cell-based antibody assays. Brain single-photon emission computed tomography detected a significant increase in blood flow in the fastigial nucleus, a critical region for eye saccade control. Immunotherapies diminished the ocular flutter and reduced hyperperfusion in the fastigial nucleus. This case suggests that autoimmune GFAP astrocytopathy can cause ocular flutter and provides strong imaging evidence supporting the hypothesis that ocular flutter is caused by hyperactivity or disinhibition of the fastigial nucleus.

[An anti-RNP antibody-positive case of aseptic meningitis induced by non-steroidal anti-inflammatory drugs in a young woman].

A 19-year-old woman developed high fever, headache, and nausea after taking Loxoprofen for pharyngitis, followed by disturbed consciousness and nuchal stiffness. The patient and her mother had a history of Raynaud's phenomenon. Cerebrospinal fluid (CSF) examination indicated a diagnosis of aseptic meningitis and revealed high levels of Q albumin and IgG index. Anti-RNP antibodies were positive in serum and CSF. Her symptoms disappeared immediately after cessation of Loxoprofen and a drug lymphocyte stimulation test was negative, confirming a diagnosis of non-steroidal anti-inflammatory drugs (NSAIDs)-induced aseptic meningitis. It should be kept in mind that an immune abnormality such as serum and CSF anti-RNP antibodies may play a role in development of NSAIDs-induced aseptic meningitis. A history of usage of NSAIDs and a thorough examination of collagen diseases are useful for identification of the origin of aseptic meningitis in a young woman.

Acute spinal subdural hematoma in a patient with active systemic lupus erythematosus: a case report and literature review.

We herein describe a case of acute spinal subdural hematoma (SSDH) during the administration of high-dose corticosteroids and intravenous heparin for the treatment of active lupus nephritis. After SSDH was promptly diagnosed using magnetic resonance imaging (MRI), the patient recovered well with conservative treatment involving the discontinuation of heparin sodium. Although SSDH is a rare complication, it should be considered as a cause of neurological manifestations in patients with active systemic lupus erythematosus.