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Introduction Pyruvate dehydrogenase complex (PDH) deficiency (Online Mendelian Inheritance in Man # 312170) is a relatively common mitochondrial disorder, caused by mutations in the X-linked PDHA1 gene and presenting with a variable phenotypic spectrum, ranging from severe infantile encephalopathy to milder chronic neurological disorders.Isolated peripheral neuropathy as predominant clinical presentation is uncommon. Results We report on a patient, now 21 years old, presenting at the age of 2 years with recurrent symmetric weakness as first symptom of a PDH deficiency. Neurophysiological evaluation proving a sensory-motor polyneuropathy with conduction blocks and presence of elevated cerebrospinal fluid proteins, suggested a chronic inflammatory demyelinating polyneuropathy. The evidence of high serum lactate and the alterations in oxidative metabolism in muscle biopsy pointed toward the final diagnosis. After starting nutritional supplements, no further episodes occurred. A hemizygous mutation in PDHA1 (p.Arg88Cys) was identified. This mutation has been previously described in five patients with a similar phenotype. A three-dimensional reconstruction demonstrated that mutations affecting this arginine destabilize the interactions between the subunits of the E1 complex. Conclusion We summarize the clinical and genetic characteristics of one patient with PDH deficiency presenting isolated peripheral nervous system involvement. This study highlights that the diagnosis of PDH deficiency should be considered in children with unexplained peripheral neuropathy, even with features suggestive of acquired forms, especially in case of early onset and limited response to treatment. A simple analysis of lactic acid could help to target the diagnosis.In addition, we suggest that the residue Arg88 is the most frequently involved in this specific phenotype of PDH deficiency.

Cardiomyopathies are mostly determined by genetic mutations affecting either cardiac muscle cell structure or function. Nevertheless, cardiomyopathies may also be part of complex clinical phenotypes in the spectrum of neuromuscular (NMD) or mitochondrial diseases (MD). The aim of this study is to describe the clinical, molecular, and histological characteristics of a consecutive cohort of patients with cardiomyopathy associated with NMDs or MDs referred to a tertiary cardiomyopathy clinic. Consecutive patients with a definitive diagnosis of NMDs and MDs presenting with a cardiomyopathy phenotype were described. Seven patients were identified: two patients with ACAD9 deficiency (Patient 1 carried the c.1240C>T (p.Arg414Cys) homozygous variant in ACAD9; Patient 2 carried the c.1240C>T (p.Arg414Cys) and the c.1646G>A (p.Ar549Gln) variants in ACAD9); two patients with MYH7-related myopathy (Patient 3 carried the c.1325G>A (p.Arg442His) variant in MYH7; Patient 4 carried the c.1357C>T (p.Arg453Cys) variant in MYH7); one patient with desminopathy (Patient 5 carried the c.46C>T (p.Arg16Cys) variant in DES); two patients with mitochondrial myopathy (Patient 6 carried the m.3243A>G variant in MT-TL1; Patient 7 carried the c.253G>A (p.Gly85Arg) and the c.1055C>T (p.Thr352Met) variants in MTO1). All patients underwent a comprehensive cardiovascular and neuromuscular evaluation, including muscle biopsy and genetic testing. This study described the clinical phenotype of rare NMDs and MDs presenting as cardiomyopathies. A multidisciplinary evaluation, combined with genetic testing, plays a main role in the diagnosis of these rare diseases, and provides information about clinical expectations, and guides management.

Background: Mitochondrial tRNA (MTT) genes are hotspot for mitochondrial DNA mutation and are responsible of half mitochondrial disease. MTT mutations are associated with a broad spectrum of phenotype often with complex multisystem involvement and complex genotype-phenotype correlations. MT-TL1 mutations, among which the m.3243A>G mutation is the most frequent, are associated with myopathy, maternal inherited diabetes and deafness, MELAS, cardiomyopathy, and focal segmental glomerulosclerosis. Case study: Here we report the case of an Italian 49-years old female presenting with encephalomyopathy, chronic proteinuric kidney disease and a new heteroplasmic m.3274_3275delAC MT-TL1 gene mutation. Conclusions: Our case demonstrates a systemic mitochondrial disease caused by the heteroplasmic m.3274_3275delAC MT-TL1 gene mutation, not yet described in the literature. A mitochondrial disease should be suspected in case of complex multisystem phenotypes, including steroid-resistant nephrotic syndrome with multisystemic involvement.

Background Pathogenic variants in the dynamin 1 like gene are related to abnormal mitochondrial dynamics and distributions and are associated to variable clinical phenotypes. A few patients harboring the p.Arg403Cys missense variant appears to be different from the classical, more severe phenotypes, showing sudden onset of drug resistant seizures after a previously normal or slightly delayed development. Case report We report on a boy with abrupt onset of focal status and coma at the age of 13, initially treated as autoimmune encephalitis, with final diagnosis of de novo missense p.Arg403Cys variant in the DNM1L gene. Discussion We compare his clinical, electrophysiological, biochemical, neuroradiological and histopathological picture to the rare cases reported to date and provide diagnostic clues that can help clinicians in differentiate p.Arg403Cys-related phenotype from that of immune-mediated encephalopathies. Conclusion The clinical picture related to p.Arg403Cys mutations should be considered alongside acquired pathologies in the differential diagnosis of young patients with focal refractory epilepsy and encephalopathy, also occurring during late childhood or adolescence. Prompt genetic testing allows to avoid unnecessary treatments and procedures and to better define the prognosis and management strategies.

RTN4IP1 pathogenic variants (OPA10 syndrome) have been described in patients with early-onset recessive optic neuropathy and recently associated with a broader clinical spectrum, from isolated optic neuropathy to severe encephalopathies with epilepsy. Here we present a case of a patient with a complex clinical picture characterized by bilateral optic nerve atrophy, horizontal nystagmus, myopia, mild intellectual disability, generalized chorea, isolated small subependymal heterotopia, and asynchronous self-resolving midbrain MRI (magnetic resonance imaging) lesions. By using massive gene sequencing, we identified in this patient the c.308G > A (p.Arg103His) homozygous pathogenic variant in the RTN4IP1 gene. Complex movement disorders and relapsing-remitting neuroradiological lesions have not been previously reported in this condition. Our case expands the clinical spectrum of OPA10 syndrome and opens new opportunities for the molecular diagnosis.

Dominant Optic Atrophy and Deafness (DOAD) may be associated with one or more of the following disorders such as myopathy, progressive external ophthalmoplegia, peripheral neuropathy, and cerebellar atrophy ("DOA-plus"). Intra- and interfamilial variability of the "DOA-plus" phenotype is frequently observed in the majority of the patients carrying the same mutation in the OPA1 gene. We are describing two familial cases of "DOA-plus" carrying the same c.1334G>A (p.Arg445His) mutation in OPA1 and disclosing different clinical, pathological and biochemical features. The two patients showed different expression levels of the mitochondrial OMI/HTRA2 molecule, which acts as a mitochondrial stress sensor and has been described to interplay with OPA1 in in vitro studies. Our data offer the cue to inquire the role of OMI/HTRA2 as a modifier gene in determining the "DOAplus" phenotype variability.

Mitochondrial tRNAs are responsible for more than half of pathogenic point mutations in the mitochondrial genome (mtDNA). Different mutations give rise to widely differing phenotypes, ranging from isolated organ-specific diseases to multisystem conditions. Herein, we report a 40-year-old woman presenting with a complex multisystem phenotype including sensorineural hearing loss, retinopathy, severe dilated cardiomyopathy, non-insulin dependent diabetes mellitus, and renal failure. Sequence analysis of mtDNA identified the m.5522G>A mutation in MT-TW, the gene encoding mitochondrial tRNA for tryptophan. The heteroplasmic variant, thus far described once, was almost exclusively confined to skeletal muscle tissue, as shown by massive parallel sequencing and corroborated by an ad hoc designed PCR-based strategy. This patient, presenting a severe, multisystem involvement apparently sparing the brain, contributes to the genetic heterogeneity of mitochondrial diseases caused by mutations in mitochondrial tRNAs.

Mitochondrial diseases (MDs) are a large group of genetically determined multisystem disorders, characterized by extreme phenotypic heterogeneity, attributable in part to the dual genomic control (nuclear and mitochondrial DNA) of the mitochondrial proteome. Advances in next-generation sequencing technologies over the past two decades have presented clinicians with a challenge: to select the candidate disease-causing variants among the huge number of data provided. Unfortunately, the clinical tools available to support genetic interpretations still lack specificity and sensitivity. For this reason, the diagnosis of MDs continues to be difficult, with the new “genotype first” approach still failing to diagnose a large group of patients. With the aim of investigating possible relationships between clinical and/or biochemical phenotypes and definitive molecular diagnoses, we performed a retrospective multicenter study of 111 pediatric patients with clinical suspicion of MD. In this cohort, the strongest predictor of a molecular (in particular an mtDNA-related) diagnosis of MD was neuroimaging evidence of basal ganglia (BG) involvement. Regression analysis confirmed that normal BG imaging predicted negative genetic studies for MD. Psychomotor regression was confirmed as an independent predictor of a definitive diagnosis of MD. The findings of this study corroborate previous data supporting a role for neuroimaging in the diagnostic approach to MDs and reinforce the idea that mtDNA sequencing should be considered for first-line testing, at least in specific groups of children.

The heterogeneous group of mitochondrial disorders (MDs) is by far the largest class of inborn errors of metabolism, having a collective incidence of 1.6 in 5000.1 Over the past decade, routine clinical use of next-generation sequencing (NGS) has allowed a considerable number of cases to receive a precise molecular diagnosis. At present, however, NGS approaches, including targeted multigene panels and exome sequencing, still fail to achieve molecular definition in about half of patients with MD with a confirmed biochemical and clinical diagnosis.2 These unresolved cases could be due to new (‘hyper-rare’) genes/loci; alternatively, they could be linked to limits of current NGS strategies: indeed, mosaicisms requiring high sequencing depth for detection, genomic rearrangements including small and large deletions/insertions ( 50 bp, respectively), and structural changes such as chromosomal rearrangements (inversions, translocations, deletions, duplications) all usually escape traditional NGS analysis pipelines. The chronic limited use of whole-genome sequencing in diagnostic settings may contribute to the substantial number of unresolved cases. The presence of repeat expansions and variants in deep intronic and regulatory regions2 may also provide an explanation for ‘missing heritability’. Although relatively rare, UPD might explain the unsolved transmission of homozygous mutations or aberrant patterns of imprinting,3 even in MDs. Here, we describe the cases of two children, each with a clinical diagnosis of MD, in whom chromosomal microarray analysis (CMA) allowed detection of UPD and helped to substantiate a homozygous variant identified by NGS. This study was conducted in accordance with Italian National Health System guidelines and the Declaration of Helsinki. Patient 1 is a child who, when first seen by us, presented with generalised tonic-clonic seizures, hypotonia and …

We sequenced the mitochondrial genome from a 40-year-old woman with myoclonus epilepsy, retinitis pigmentosa, leukoencephalopathy and cerebral calcifications. Histological and biochemical features of mitochondrial respiratory chain dysfunction were present. Direct sequencing showed a novel heteroplasmic mutation at nucleotide 5513 in the MT-TW gene that encodes tRNATrp. Restriction Fragment Length Polymorphism analysis confirmed that about 80% of muscle mtDNA harboured the mutation while it was present in minor percentages in mtDNA from other tissues. The mutation is predicted to disrupt a highly conserved base pair within the aminoacyl acceptor stem of the tRNA. This is the 17° mutation in MT-TW gene and expands the known causes of late-onset mitochondrial diseases.

Objective:To describe a second hereditary sensory autonomic neuropathy type VI (HSAN-VI) family harboring 2 novel heterozygous mutations in the dystonin (DST) gene and to evaluate their effect on neurons derived from induced pluripotent stem cells (iPSC).Methods:The family consisted of 3 affected siblings from nonconsanguineous healthy parents. All members underwent clinical and electrophysiologic evaluation and genetic analysis. Two patients underwent quantitative sensory testing (QST), cardiovascular reflexes, dynamic sweat test, and skin biopsy to evaluate somatic and autonomic cutaneous innervation and to get fibroblast cultures for developing iPSC-derived neurons.Results:Onset occurred in the first decade, with painless and progressive mutilating distal ulcerations leading to amputation and joint deformity. Sensation to pain, touch, and vibration was reduced. Autonomic disturbances included hypohidrosis, pupillary abnormalities, and gastrointestinal and sexual dysfunction. Nerve conduction studies showed a severe axonal sensory neuropathy. QST and autonomic functional studies were abnormal. Skin biopsy revealed a lack of sensory and autonomic nerve fibers. Genetic analysis revealed 2 pathogenic mutations in the DST gene affecting exclusively the DST neuronal isoform-a2. Neurons derived from iPSC showed absence or very low levels of DST protein and short and dystrophic neuritis or no projections at all.Conclusions:Unlike the previous HSAN-VI family, our description indicates that DST mutations may be associated with a nonlethal and nonsyndromic phenotype. Neuronal loss affects large and small sensory nerve fibers as well as autonomic ones. Induced-PSC findings suggest that dystonin defect might alter proper development of the peripheral nerves. Dystonin-a2 plays a major role in the HSAN-VI phenotype.

Aim: Owing to their catalytic properties as reactive oxygen species scavengers, cerium oxide nanoparticles (nanoceria) have become an extremely promising candidate for medical applications, especially in the treatment of diseases where oxidative stress has been proposed as one of the main pathogenesis factors. Materials & methods: In this work, nanoceria antioxidant power has been tested in primary cultured skin fibroblasts, derived from healthy individuals, by evaluating the mitochondrial function both in basal condition and after an oxidative insult. Results & conclusion: Combined with a clear lack of toxicity, antioxidant activity makes nanoceria promising in a wide range of clinical applications sharing the common signature of a global bioenergetic dysfunction.

Mitochondrial ribosomal protein large 24 (MRPL24) is 1 of the 82 protein components of mitochondrial ribosomes, playing an essential role in the mitochondrial translation process. We report here on a baby girl with cerebellar atrophy, choreoathetosis of limbs and face, intellectual disability and a combined defect of complexes I and IV in muscle biopsy, caused by a homozygous missense mutation identified in MRPL24. The variant predicts a Leu91Pro substitution at an evolutionarily conserved site. Using human mutant cells and the zebrafish model, we demonstrated the pathological role of the identified variant. In fact, in fibroblasts we observed a significant reduction of MRPL24 protein and of mitochondrial respiratory chain complex I and IV subunits, as well a markedly reduced synthesis of the mtDNA-encoded peptides. In zebrafish we demonstrated that the orthologue gene is expressed in metabolically active tissues, and that gene knockdown induced locomotion impairment, structural defects and low ATP production. The motor phenotype was complemented by human WT but not mutant cRNA. Moreover, sucrose density gradient fractionation showed perturbed assembly of large subunit mitoribosomal proteins, suggesting that the mutation leads to a conformational change in MRPL24, which is expected to cause an aberrant interaction of the protein with other components of the 39S mitoribosomal subunit.

CLN5 disease is a rare form of late-infantile neuronal ceroid lipofuscinosis (NCL) caused by mutations in the CLN5 gene that encodes a protein whose primary function and physiological roles remains unresolved. Emerging lines of evidence point to mitochondrial dysfunction in the onset and progression of several forms of NCL, offering new insights into putative biomarkers and shared biological processes. In this work, we employed cellular and murine models of the disease, in an effort to clarify disease pathways associated with CLN5 depletion. A mitochondria-focused quantitative proteomics approach followed by functional validations using cell biology and immunofluorescence assays revealed an impairment of mitochondrial functions in different CLN5 KO cell models and in Cln5−/− cerebral cortex, which well correlated with disease progression. A visible impairment of autophagy machinery coupled with alterations of key parameters of mitophagy activation process functionally linked CLN5 protein to the process of neuronal injury. The functional link between impaired cellular respiration and activation of mitophagy pathways in the human CLN5 disease condition was corroborated by translating organelle-specific proteome findings to CLN5 patients’ fibroblasts. Our study highlights the involvement of CLN5 in activation of mitophagy and mitochondrial homeostasis offering new insights into alternative strategies towards the CLN5 disease treatment.

Mutations in the ATPase family 3‐like gene (AFG3L2) have been linked to autosomal‐dominant spinocerebellar ataxia type 28 and autosomal recessive spastic ataxia‐neuropathy syndrome. Here, we describe the case of a child carrying bi‐allelic mutations in AFG3L2 and presenting with ictal paroxysmal episodes associated with neuroimaging suggestive of basal ganglia involvement. Studies in skin fibroblasts showed a significant reduction of AFG3L2 expression. The relatively mild clinical presentation and the benign course, in spite of severe neuroimaging features, distinguish this case from data reported in the literature, and therefore expand the spectrum of neurological and neuroradiological features associated with AFG3L2 mutations.

Perrault syndrome is a rare disorder characterized by ovarian dysgenesis, bilateral sensorineural hearing loss and associated with mutations in six mitochondrial proteins. Additional neurological features were also described. Herein, we report on a 27-year-old woman with Perrault syndrome (PS), moderate ataxia and axonal sensory-motor peripheral neuropathy in whom we identified compound heterozygous mutations in the TWNK gene (p.Val507Ile and the novel p.Phe248Ser variant). Fewer than 30 patients with PS have been reported worldwide. Neurological involvement is more frequently associated with mutations in TWNK and indicates possible genotype-phenotype correlations. TWNK mutations should be searched in patients with sensory ataxia, early onset bilateral sensorineural hearing loss, and ovarian dysfunction in women.

TSFM is a nuclear gene encoding the elongation factor Ts (EFTs), an essential component of mitochondrial translational machinery. Impaired mitochondrial translation is responsible for neurodegenerative disorders characterized by multiple respiratory chain complex defects, multisystemic involvement, and neuroradiological features of Leigh-like syndrome. With the use of a next-generation sequencing (NGS)-based multigene panel for mitochondrial disorders, we identified the novel TSFM homozygous variant c.547G>A (p.Gly183Ser) in a 5-year-old boy with infantile early onset encephalocardiomyopathy, sensorineural hearing loss, and peculiar partially reversible neuroimaging features. Our findings expand the phenotypic spectrum of TSFM-related encephalopathy, offering new insights into the natural history of brain involvement and suggesting that TSFM should be investigated in pediatric mitochondrial disorders with distinctive neurologic and cardiac involvement.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is an early-onset neurodevelopmental disorder characterized by the association of spastic ataxia and sensorimotor neuropathy. Additional features include retinal changes and cognitive impairment. Today, next-generation sequencing (NGS) techniques are allowing the rapid identification of a growing number of missense variants, even in less typical forms of the disease, but the pathogenic significance of these changes is often difficult to establish on the basis of classic bioinformatics criteria and genotype/phenotype correlations. Herein, we describe two novel cases of missense mutations in SACS. The two individuals were identified during the genetic screening of a large cohort of patients with inherited ataxias. We discuss how protein studies and specialized ophthalmological investigations could represent useful pointers for the interpretation of genetic data. Combination of these tools with NGS for rapid genotyping might help to identify new true ARSACS cases.

Complex I (CI) is the largest component of the mitochondrial respiratory chain (MRC) and it is made up of 7 mitochondrial DNA (mtDNA)-encoded and at least 38 nuclear DNA-encoded subunits. Isolated CI deficiency is the most common single enzyme deficiency in the heterogeneous group of MRC disorders and it is a relatively common etiology of Leigh-like syndrome (LS). With a few exceptions, descriptions of the clinical spectrum of specific mutations in CI are scarce. We here present three unrelated Italian children who harbored the homoplasmic m.10197G>A mutation in MT-ND3 associated with reduced enzyme activity of CI in muscle. Compared with the spectrum of phenotypes seen in 13 previously described families with the same mutation, these children showed some novel clinical features. Two of the boys presented with subacute onset of dystonia, which showed a remitting-relapsing clinical course in one of them. The third boy presented acute symptoms consisting of speech impairment, progressive left-sided hemiparesis, and also vertebral and arterial malformations. In all the children, molecular studies identified a similar mutation load in tissues, and neuroimaging findings were consistent with the features seen in LS. Functional investigations in cultured skin fibroblasts suggested low ATP production in homoplasmic cells. Our results confirm that the m.10197G>A mutation is relevant to these patients' clinical and biochemical phenotypes, which thus expand the array of phenotypes associated with this variant.

Introduction: There are several reported cases of patients developing motor and cognitive neurological impairment under treatment with valproic acid (VPA). We describe a woman who developed a subacute encephalopathy after VPA intake, harboring a mitochondrial DNA variant, previously described as causing VPA sensitivity in one pediatric patient. Material and Methods: A 65-year old woman developed a progressive, severe neurological deterioration after a 3 month treatment with valproate sodium, 800 mg daily. Magnetic resonance spectroscopy (MRS), muscle histochemical analysis and assay of mitochondrial enzymatic activities, and mitochondrial DNA sequencing were performed. Results: Neurological examination showed drowsiness, vertical gaze palsy, inability to either stand or walk, diffuse weakness, increased tendon reflexes. Blood lactate was increased, EEG showed diffuse theta and delta activity, MRI subcortical atrophy and leukoencephalopathy, MRS marked reduction of the NAA spectrum, with a small signal compatible with presence of lactate. Muscle biopsy evidenced presence of ragged red fibers (20%) and reduced COX reactivity. Assay of the muscle enzymatic activities showed multiple deficiencies of the electron transport chain and reduced ATP production. The mt.8393C>T variant in the MT-ATP8 gene was found in homoplasmy. The patient considerably improved after valproate withdrawal. Conclusion: The variant we found has been reported both as a polymorphism and, in a single patient, as related to the valproate-induced encephalopathy. The present case is the first bearing this mutation in homoplasmy. In case of neurological symptoms after starting VPA therapy, once hyperammonemia and liver failure have been ruled out, mtDNA abnormalities should be considered.

Aminoacylase 1 deficiency (ACY1D) is a rare inborn error of metabolism characterized by increased urinary excretion of N-acetylated amino acids. Clinical phenotypes of 15 known patients with ACY1 deficiency have been described up to now. Findings are greatly variable, ranging from normality to relevant neurological and psychiatric impairments, but clinical follow up has been rarely reported. To partially fill this gap, we present a detailed clinical description and the outcome four years post-diagnosis of a patient already described, with mild intellectual disability, language delay, autistic traits and compound heterozygous mutations in ACY1.

A 7-year-old boy was referred at age 24 months with failure to thrive, global psychomotor delay, and spastic-ataxic gait with bilateral Babinski sign. Last examination revealed a further psychomotor regression and low IQ. The child could not talk, sit, or walk autonomously and showed upper limb dystonia. His Spastic Paraplegia Rating Scale1 score was 35/52.

Myoclonus is a possible manifestation of mitochondrial disorders, and its presence is considered, in association with epilepsy and the ragged red fibers, pivotal for the syndromic diagnosis of MERRF (myoclonic epilepsy with ragged red fibers). However, its prevalence in mitochondrial diseases is not known. The aims of this study are the evaluation of the prevalence of myoclonus in a big cohort of mitochondrial patients and the clinical characterization of these subjects. Based on the database of the "Nation-wide Italian Collaborative Network of Mitochondrial Diseases," we reviewed the clinical and molecular data of mitochondrial patients with myoclonus among their clinical features. Myoclonus is a rather uncommon clinical feature of mitochondrial diseases (3.6% of 1,086 patients registered in our database). It is not strictly linked to a specific genotype or phenotype, and only 1 of 3 patients with MERRF harbors the 8344A>G mutation (frequently labeled as "the MERRF mutation"). Finally, myoclonus is not inextricably linked to epilepsy in MERRF patients, but more to cerebellar ataxia. In a myoclonic patient, evidences of mitochondrial dysfunction must be investigated, even though myoclonus is not a common sign of mitochondriopathy. Clinical, histological, and biochemical data may predict the finding of a mitochondrial or nuclear DNA mutation. Finally, this study reinforces the notion that myoclonus is not inextricably linked to epilepsy in MERRF patients, and therefore the term "myoclonic epilepsy" seems inadequate and potentially misleading.

Behr syndrome is characterized by the association of early onset optic atrophy, cerebellar ataxia, pyramidal signs, peripheral neuropathy and mental retardation. Recently, some cases were reported to be caused by biallelic mutations in OPA1 . We describe an 11-year-old girl (Pt1) and a 7-year-old boy (Pt2) with cognitive delay, ataxic gait and clinical signs suggestive of a peripheral neuropathy, with onset in early infancy. In Pt1 ocular fundus examination revealed optic disk pallor whereas Pt2 exhibited severe optic atrophy. In both children neuroimaging detected a progressive cerebellar involvement accompanied by basal ganglia hyperintensities and pathological peak levels of lactate. In both patients, muscle biopsy showed diffuse reduction of cytochrome c oxidase stain, some atrophic fibers and type II fiber grouping. Using a targeted resequencing panel in next generation sequencing, we identified the homozygous c.1180G>A/p.Ala394Thr mutation in Pt1 and the c.2779-2A>C mutation in compound heterozygosity with the c.2809C>T/p.Arg937Cys mutation in Pt2. All variants were novel and segregated in the healthy parents. Expression of OPA1 protein was significantly reduced in muscle tissues of both patients by Western blotting. We also observed in patients' fibroblasts a higher proportion of fragmented and intermediate mitochondria upon galactose treatment compared to controls, as already seen in other patients harboring mutations in OPA1 . The presence of Leigh-like neuroimaging features is a novel finding in Behr syndrome and further adds to the complex genotype–phenotype correlations in OPA1 -associated disorders.

Leigh syndrome (LS) is an early-onset progressive neurodegenerative disorder, characterized by a wide clinical and genetic heterogeneity, and is the most frequent disorder of mitochondrial energy production in children. Beside its great variability in clinical, biochemical, and genetic features, LS is pathologically uniformly characterized by multifocal bilateral and symmetric spongiform degeneration of the basal ganglia, brainstem, thalamus, cerebellum, spinal cord, and optic nerves. Isolated complex I deficiency is the most common defect identified in Leigh syndrome. In 2011, the first child with a mutation of NDUFA10 gene, coding for an accessory subunits of complex I, was described. Here, we present an additional description of a child with Leigh syndrome harboring a homozygous mutation in NDUFA10, providing insights in clinical, biochemical, and neuroradiologic features for future earlier recognition.

To describe a second hereditary sensory autonomic neuropathy type VI (HSAN-VI) family harboring 2 novel heterozygous mutations in the dystonin (The family consisted of 3 affected siblings from nonconsanguineous healthy parents. All members underwent clinical and electrophysiologic evaluation and genetic analysis. Two patients underwent quantitative sensory testing (QST), cardiovascular reflexes, dynamic sweat test, and skin biopsy to evaluate somatic and autonomic cutaneous innervation and to get fibroblast cultures for developing iPSC-derived neurons.Onset occurred in the first decade, with painless and progressive mutilating distal ulcerations leading to amputation and joint deformity. Sensation to pain, touch, and vibration was reduced. Autonomic disturbances included hypohidrosis, pupillary abnormalities, and gastrointestinal and sexual dysfunction. Nerve conduction studies showed a severe axonal sensory neuropathy. QST and autonomic functional studies were abnormal. Skin biopsy revealed a lack of sensory and autonomic nerve fibers. Genetic analysis revealed 2 pathogenic mutations in theUnlike the previous HSAN-VI family, our description indicates that

A 49-year-old man presented with chest pain, dyspnea, and lactic acidosis. Left ventricular hypertrophy and myocardial fibrosis were detected. The sequencing of mitochondrial genome (mtDNA) revealed the presence of A to G mtDNA point mutation at position 3243 (m.3243A>G) in tRNALeu(UUR) gene. Diagnosis of cardiac involvement in a patient with Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes syndrome (MELAS) was made. Due to increased risk of sudden cardiac death, cardioverter defibrillator was implanted.

Background: Myelinated retinal nerve fibers are considered a hallmark of autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) in French Canadian patients. The demonstration of a worldwide distribution of this disease, as well as the almost invariable presence of a normal retina on fundoscopy in cases outside Canada, suggests that more quantitative methodologies are needed to assess the retina in ARSACS. Methods: To characterize better the retinal features of ARSACS, we studied five Italian patients by means of optical coherence tomography (OCT), a processing method that allows the creation of three-dimensional images with micrometer resolution. We compared OCT characteristics in ARSACS with those obtained from five subjects with persistent myelination of the retina, a rare congenital non-progressive anomaly. Results: Four patients with ARSACS showed myelinated retinal nerve fibers on ophthalmoscopy, corresponding to an increased thickness of the retina on OCT, a characteristic not present in the subjects with persistent myelination of the retina. Conclusions: Myelinated retinal fibers are not rare in Italian patients with ARSACS. This finding may be the consequence of the thickening of the retina, as detected by OCT.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the progressive death of substantia nigra dopaminergic neurons that results in a regional loss of striatal dopamine (DA) levels. Dental pulp contains ex vivo-expandable cells called dental pulp stem cells (DPSCs), with the capacity to differentiate into multiple cell lineages. More interestingly, due to their embryonic origin, DPSCs express neurotrophic factors such as brain-derived neurotrophic factor, nerve growth factor and glial cell-derived neurotrophic factor. The aim of the present study was to investigate the neuroprotective effects of DPSCs against MPP+ (2.5, 5, and 10 μM) and rotenone (0.25, 0.5 and 1 μM) in an in vitro model of PD, using an indirect co-culture system with mesencephalic cell cultures. When mesencephalic cultures were challenged with MPP+ or rotenone, in the presence of DPSCs a statistically significant protective effect was observed at all the tested doses in terms of DA uptake. DPSCs protective effect on DA neurons was also confirmed by immunocytochemistry: an increased number of spared tyrosine hydroxylase (TH)+ cells was observed in co-culture conditions compared to controls, and neurons showed longer processes in comparison with mesencephalic cells grown without DPSCs. In conclusion, the co-culture with DPSCs significantly attenuated MPP+ or rotenone-induced toxicity in primary cultures of mesencephalic neurons. Considering that the direct contact between the two cell types was prevented, it can be speculated that neuroprotection could be due to soluble factors such as BDNF and NGF, released by DPSCs. Blocking BDNF and NGF with neutralizing antibodies, the neuroprotecting effect of DPSCs was completely abolished. Therefore DPSCs can be viewed as possible candidates for studies on cell-based therapy in neurodegenerative disorders.

We report a novel heteroplasmic mitochondrial DNA mutation in the tRNA gene at nucleotide 7458 (m.7458GA) in a 26-year-old patient affected with sporadic progressive external ophthalmoplegia associated with dysphagia. Muscle biopsy showed a strong succinate dehydrogenase staining, ragged red fibers, and 15% of cytochrome c oxidase-negative fibers. Activities of mitochondrial respiratory chain complexes I+III and IV were reduced. The mutation was heteroplasmic (75%) in the muscle, but undetectable in accessible tissues from the patient and his maternal relatives. This report expands the molecular heterogeneity of progressive external ophthalmoplegia.

Mitochondrial ATP synthase plays a central role in cell function by synthesising most of the ATP in human tissues. In different cells, active regulation of mitochondrial ATP synthase in response to cellular energy demand has been demonstrated, as well as its alteration under several pathological conditions affecting oxidative phosphorylation (OXPHOS). Traditionally, detection of OXPHOS defects is based on the spectrophotometric measurement of respiratory chain complex activities in muscle biopsies. Considering the broad clinical spectrum of mitochondrial disorders, and the difficulty in arriving at a single diagnostic method, in this study we propose measurement of ATP synthesis in mitochondria from skin fibroblasts as an effective screening tool. In the light of our results this assessment emerges as a useful marker of impaired energy production in primary OXPHOS disorders of childhood and as a tool with the potential to drive further molecular genetic studies.