In recent years, an autoantibody directed against the 5′-citosolic nucleotidase1A (cN1A) was identified in the sera of sporadic inclusion body myositis (s-IBM) patients with widely variable sensitivity (33%–76%) and specificity (87%–100%). We assessed the sensitivity/specificity of anti-cN1A antibodies in an Italian cohort of s-IBM patients, searching for a potential correlation with clinical data. We collected clinical data and sera from 62 consecutive s-IBM patients and 62 other inflammatory myopathies patients. Testing for anti-cN1A antibodies was performed using a commercial ELISA. Anti-cN1A antibodies were detected in 23 s-IBM patients, resulting in a sensitivity of 37.1% with a specificity of 96.8%. Positive and negative predictive values were 92.0% and 60.6%, respectively. We did not find significant difference regarding demographic variables, nor quadriceps or finger flexor weakness. Nevertheless, we found that anti-cN1A-positive patients presented significantly lower scores in IBMFRS item 1 (swallowing, p = 0.045) and more frequently reported more severe swallowing problems, expressed as an IBMFRS item 1 score ≤ 2 (p < 0.001). We confirmed the low sensitivity and high specificity of anti-cN1A Ab in s-IBM patients with a high positive predictive value. The presence of anti-CN1A antibodies identified patients with a greater risk of more severe dysphagia.

We report on a sporadic patient suffering Leigh syndrome characterized by bilateral lesions in the lenticular nuclei and spastic dystonia, intellectual disability, sensorineural deafness, hypertrophic cardiomyopathy, exercise intolerance, and retinitis pigmentosa. Complete sequencing of mitochondrial DNA revealed the heteroplasmic nucleotide change m.15635T>C affecting a highly conserved amino acid position (p.Ser297Pro) in the cytochrome b (MT-CYB) gene on a haplogroup K1c1a background, which includes a set of four non-synonymous polymorphisms also present in the same gene. Biochemical studies documented respiratory chain impairment due to complex III defect. This variant fulfils the criteria for being pathogenic and was previously reported in a sporadic case of fatal neonatal polyvisceral failure.

Background and Objectives To date, approximately 20 heterozygous mainly loss-of-function variants in KCND3 have been associated with spinocerebellar ataxia (SCA) type 19 and 22, a clinically heterogeneous group of neurodegenerative disorders. We aimed at reporting the second patients with the V374A KCND3 mutation from an independent family, confirming its pathogenic role. Methods We describe the clinical history of a patient with SCA and conducted genetic investigations including mitochondrial DNA analysis and exome sequencing. Results This male patient was reported to have unstable gait with tremors at the lower limbs and dysarthric speech since childhood. A neurologic examination also showed dysarthria, nystagmus, action tremor, dysmetria, and weak deep tendon reflexes. He had marked cerebellar atrophy at brain MRI, more evident at vermis. Molecular analysis, including exome sequencing and an in silico panel analysis of genes associated with SCA, revealed the c.1121T>C [p.V374A] mutation in KCND3. Discussion This report consolidates the pathogenicity of the V374A KCND3 mutation and suggests that the ataxic paroxysmal exacerbations are not a key phenotypic feature of this mutation.

We present a comprehensive molecular and histopathological characterization of nine patients with mitochondrial myopathy, predominantly manifesting progressive external ophthalmoplegia (PEO), associated with heteroplasmic variants in mitochondrial tRNA genes (mt-tRNA). Among the ten variants identified, four were novel and previously unreported in MITOMAP. Using laser capture microdissection and deep next-generation sequencing, we quantified heteroplasmy at the single-muscle-fibre level, demonstrating that cytochrome c oxidase (COX)–deficient fibres consistently reached near-homoplasmic mutant loads, whereas COX-positive fibres remained heteroplasmic with lower variant fractions. These findings firmly support the pathogenic role of all variants. Furthermore, digital droplet PCR revealed an increased mitochondrial DNA (mtDNA) content in COX-deficient fibres, indicating compensatory mitochondrial biogenesis. Of particular note, one patient harboured two novel heteroplasmic variants, m.10009G > A and m.15961G > A, for which long-read sequencing identified mitogenomes carrying both variants also in cis, suggesting the occurrence of mtDNA recombination in human tissue. By applying refined American College of Medical Genetics and Genomics (ACMG) criteria specific for mt-tRNA, we reclassified several variants as pathogenic or likely pathogenic, including three previously deemed of uncertain significance. Overall, our integrative approach—combining single-fibre molecular dissection, mtDNA quantification, and long-read sequencing—broadens the mutational spectrum of pathogenic mt-tRNA variants, highlights the diagnostic value of single-fibre analyses in confirming pathogenicity, and provides new insights into mitochondrial genome dynamics and compensatory responses in mitochondrial disease.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with a complex genetic architecture, showing monogenic, oligogenic, and polygenic inheritance. In this study, we describe the case of a 71 years-old man diagnosed with ALS with an atypical phenotype, due to the presence of a progressive ocular ptosis. Genetic analyses revealed two variants in SOD1 and TBK1 genes respectively and the LHON-associated m.14484T>C variant in the mitochondrial DNA (mtDNA). We discuss how all these variants may synergically impinge on mitochondrial function, contributing to the pathogenic mechanisms which might ultimately lead to the neurodegenerative process, possibly influencing the clinical ALS phenotype.