Familial Psychomotor Delay of an Uncommon Cause: Type II Congenital Methemoglobinemia.

Methemoglobinemia is due to oxidization of divalent ferro-iron of hemoglobin to ferri-iron of methemoglobin (MetHb) which is incapable of transferring oxygen to tissues. This disease may be acquired by intoxication with oxidizing agents or inherited with a mutation of CYB5R3, the gene coding for the methemoglobin reductase or cytochrome B5 reductase 3 responsible for the reduction of MetHb to hemoglobin. We report the case of 2 sisters aged respectively of 15 and 8 months. They were born to a second-degree consanguineous marriage with a history of precocious and unexplained deaths in 3 relatives. Both sisters presented neurological features including psychomotor retardation, microcephaly, and axial hypotonia. Cerebral magnetic resonance imaging revealed cerebral atrophy in both cases associated with hypoplasia of the corpus callosum in the younger child. The association of neurological disability, cyanosis, and hypoxemia prompted a search for methemoglobinemia, with MetHB levels respectively of 26% and 15.8%in the 2 sisters. Initial treatment was based on methylene blue, then ascorbic acid. The genetic study revealed a c.463+8G>C mutation of CYB5R3 confirming the diagnosis of methemoglobinemia type II. The diagnosis of methemoglobinemia, although rare, should be considered in the presence of psychomotor retardation with cyanosis and subacute onset hypoxemia, especially in the presence of a family history.

Clinical details of individuals with Rauch-Steindl syndrome due to NSD2 truncating variants.

BACKGROUND: Rauch-Steindl syndrome (RAUST) is a very rare genetic syndrome caused by a pathogenic variant in NSD2 on chromosome 4p16.3. Although NSD2 was previously thought to be the major gene in Wolf-Hirschhorn syndrome (WHS), a contiguous gene syndrome of chromosome 4p16.3 deletion, RAUST has been found to present different facial and clinical features from WHS. In this study, we report the details of two newly diagnosed individuals with RAUST in order to better understand the molecular and clinical features of RAUST. METHODS: Whole-genome sequencing was performed on two individuals with psychomotor delay and growth failure. Detailed clinical evaluation of growth parameters, craniofacial features, electroencephalogram (EEG), magnetic resonance imaging of the brain, and developmental assessment were performed. RESULTS: Both individuals had de novo truncating variants in NSD2. One had a novel variant (c.2470C>T, p.Arg824*), and the other had a recurrent variant (c.4028del, p.Pro1343Glnfs*49). Both exhibited characteristic RAUST facial features, growth failure, and mild psychomotor delay. A novel finding of RAUST was seen in individual 2, a Chiari malformation type 1, and both showed delayed bone age. They lacked common WHS features such as congenital heart defects, cleft lip/palate, and seizures (EEG with abnormal findings). CONCLUSION: We present a novel variant and clinical presentations of RAUST, expand the molecular and clinical diversity of RAUST, and improve our understanding of this rare syndrome, which is distinct from WHS. Further researches are needed on more RAUST cases and on functional analysis of NSD2.

Phenylketonuria and the brain.

Classic phenylketonuria (PKU) is caused by defective activity of phenylalanine hydroxylase (PAH), the enzyme that coverts phenylalanine (Phe) to tyrosine. Toxic accumulation of phenylalanine and its metabolites, left untreated, affects brain development and function depending on the timing of exposure to elevated levels. The specific mechanisms of Phe-induced brain damage are not completely understood, but they correlate to phenylalanine levels and on the stage of brain growth. During fetal life, high levels of phenylalanine such as those seen in maternal PKU can result in microcephaly, neuronal loss and corpus callosum hypoplasia. Elevated phenylalanine levels during the first few years of life can cause acquired microcephaly, severe cognitive impairment and epilepsy, likely due to the impairment of synaptogenesis. During late childhood, elevated phenylalanine can cause alterations in neurological functioning, leading to ADHD, speech delay and mild IQ reduction. In adolescents and adults, executive function and mood are affected, with some of the abnormalities reversed by better control of phenylalanine levels. Altered brain myelination can be present at this stage. In this article, we review the current knowledge about the consequences of high phenylalanine levels in PKU patients and animal models through different stages of brain development and its effect on cognitive, behavioural and neuropsychological function.

Isolated neurological presentations of mevalonate kinase deficiency.

Mevalonate kinase (MK) deficiency is a rare autosomal recessive metabolic disorder caused by pathogenic variants in the MVK gene with a broad phenotypic spectrum including autoinflammation, developmental delay and ataxia. Typically, neurological symptoms are considered to be part of the severe end of the phenotypical spectrum and are reported to be in addition to the autoinflammatory symptoms. Here, we describe a patient with MK deficiency with severe neurological symptoms but without autoinflammation and we found several similar patients in the literature. Possibly, the non-inflammatory phenotype is related to a specific genotype: the MVK p.(His20Pro)/p.(Ala334Thr) variant. There is probably an underdetection of the neurological MK deficient phenotype without inflammatory symptoms as clinicians may not test for MK deficiency when patients present with only neurological symptoms. In conclusion, although rare, neurological symptoms without hyperinflammation might be more common than expected in MK deficiency. It seems relevant to consider MK deficiency in patients with psychomotor delay and ataxia, even if there are no inflammatory symptoms.

Determinants of the psychomotor development delay in children aged 12 to 59 months infected with HIV in Yaounde, Cameroon.

Introduction: children infected with HIV are at increased risk of impaired neurodevelopmental, due to several environmental factors. Methods: we conducted a cross-sectional analytical study on HIV-infected children aged 12 to 59 months, followed up in five hospitals in Yaounde, Cameroon. Sociodemographic, clinical, and biological variables as well as the antecedents were collected. Data analysis was performed using Statistical Package for the Social Sciences (SPSS) version 25 software. The Denver test was used to assess the psychomotor development of these children. Global psychomotor delay, defined as a global development quotient of less than 70 with an alteration in at least two of the four domains of the test, was retained as the primary endpoint. The significance threshold was set at 5%. Results: one hundred and eighty-one children were included in the study. The sex ratio was 0.6. The age range 48-59 months was the most represented. None of these children had a known chronic pathology other than HIV infection. The proportion of global psychomotor delay was 11.04%, with language (16%) and fine motor skills (16%) being the most affected domains of psychomotor development. The independent factors significantly associated with global psychomotor delay were birth weight below 2500 grams (OR= 17.61 [1.76-181.39], p= 0.022), growth retardation (OR= 17.64 [1.63-190.24], p= 0.018) and elevated viral load (OR= 22.75 [2.78-186.02], p= 0.004). Conclusion: psychomotor delay affects about one out of ten children living with HIV. Its occurrence is linked to various factors that must be taken into account in the development of public health policies in connection with the management of HIV infection in children.

Mitochondrial bioenergetic is impaired in Monocarboxylate transporter 1 deficiency: a new clinical case and review of the literature.

BACKGROUND: Monocarboxylate transporter 1 (MCT1) deficiency has recently been described as a rare cause of recurrent ketosis, the result of impaired ketone utilization in extrahepatic tissues. To date, only six patients with this condition have been identified, and clinical and biochemical details remain incomplete. RESULTS: The present work reports a patient suffering from severe, recurrent episodes of metabolic acidosis and psychomotor delay, showing a pathogenic loss-of-function variation c.747_750del in homozygosity in SLC16A1 (which codes for MCT1). Persistent ketotic and lactic acidosis was accompanied by an abnormal excretion of organic acids related to redox balance disturbances. Together with an altered bioenergetic profile detected in patient-derived fibroblasts, this suggests possible mitochondrial dysfunction. Brain MRI revealed extensive, diffuse bilateral, symmetric signal alterations for the subcortical white matter and basal ganglia, together with corpus callosum agenesia. CONCLUSIONS: These findings suggest that the clinical spectrum of MCT1 deficiency not only involves recurrent atacks of ketoacidosis, but may also cause lactic acidosis and neuromotor delay with a distinctive neuroimaging pattern including agenesis of corpus callosum and other brain signal alterations.

THYROID DYSFUNCTION IN PREGNANCY: COMPARISON OF OUTCOMES IN INFANTS.

The aim of this study was to compare the incidence of mild psychomotor delay in infants whose mothers were treated for thyroid dysfunction regardless of the cause during first trimester of pregnancy with those whose mothers did not use medications prenatally. The sample included 200 infants up to 4 months of age. Half of the infants were examined by a pediatric physiatrist, while the other half were chosen randomly from the primary pediatric clinic. Binary logistic regression was performed to assess the impact of factors on psychomotor delay. The model contained seven independent variables derived from bivariate analyses and clinical relevance. Results showed that the infant's chance of having psychomotor delay was 5.53 times higher if the mother had drug-compensated thyroid dysfunction. Younger gestational age increased the likelihood of delay 2.12 times per each gestational week. The likelihood of psychomotor delay also rose by 1% per 1 g of birth weight reduction. We found strong positive linear correlation between maternal drug-compensated thyroid dysfunction during pregnancy and psychomotor delay in infants, which has not been reported elsewhere. This differentiates an important and common prenatal risk factor and lays the foundation for faster initiation of habilitation of infants at risk. These insights provide a basis for planning the National Screening Program for Neurorisk Infants.

Case report: 7p22.3 deletion and 8q24.3 duplication in a patient with epilepsy and psychomotor delay-Does both possibly act to modulate a candidate gene region for the patient's phenotype?

Background: Psychomotor delay, epilepsy and dysmorphic features are clinical signs which are described in multiple syndromes due to chromosomal imbalances or mutations involving key genes implicated in the stages of Early Embryonic Development. In this context, we report a 10 years old Tunisian patient with these three signs. Our objective is to determine the cause of developmental, behavioral and facial abnormalities in this patient. Methods: We used banding cytogenetics (karyotype) and Array Comparative Genomic Hybridization (Array CGH) to this purpose. Results: The karyotype was in favor of a derivative of chromosome 7 in the patient and Array CGH analysis revealed a loss of genetic material in 7p22.3-p22.1 (4,56 Mb) with a gain at 8q24.23-q24 (9.20 Mb) resulting from maternal 7/8 reciprocal translocation. An in silico analysis of the unbalanced region was carried out and showed that the 7p22.3-p22.1 deletion contains eight genes. Among them, BRAT1 gene, previously described in several neurodevelopmental diseases, may be a candidate gene which absence could be correlated to the patient's phenotype. However, the 8q24.23-q24 duplication could be involved in the phenotype of this patient. Conclusion: In this study, we report for the first time a 7p deletion/8q duplication in a patient with psychomoteur delay, epilepsy and facial dysmorphism. Our study showed that Array CGH still useful for delivering a conclusive genetic diagnosis for patients having neurodevelopmental abnormalities in the era of next-generation sequencing.

Psychomotor Delay in a Child with FGFR3 G380R Pathogenic Mutation Causing Achondroplasia.

Achondroplasia (ACH) is a hereditary disorder of dwarfism that is caused by the aberrant proliferation and differentiation of chondrocyte growth plates. The common findings of macrocephaly and facial anomalies accompany dwarfism in these patients. Fibroblast growth factor receptor 3 ( FGFR3 ) gene mutations are common causes of achondroplasia. The current study presents a case of 2-year-old male child patient presenting with phenotypic characteristics of ACH. The interesting finding of the case is the presence of psychomotor delay that is not very common in these patients. Clinical exome sequencing analyzing 4.813 disease causing genes revealed a de novo c.1138G > A mutation within the FGFR3 gene. In conclusion, the mutation confirms the clinical diagnosis of ACH, and it seems to be causing the psychomotor delay in this patient.

General anesthesia for cesarean delivery and childhood neurodevelopmental and perinatal outcomes: a secondary analysis of a randomized controlled trial.

BACKGROUND: In 2016, the U.S. Food and Drug Administration expressed concern that neurodevelopment may be negatively affected by anesthesia or sedation exposure in pregnancy or before three years of age. We examined the association between general anesthesia at the time of cesarean delivery and early childhood neurodevelopment. METHODS: A secondary analysis of a multicenter randomized controlled trial assessing magnesium for prevention of cerebral palsy in infants at risk for preterm delivery. Exposure was general compared to neuraxial anesthesia. The primary outcome was motor or mental delay at two years of age, assessed by Bayley Scales of Infant Development II (BSIDII). Secondary outcomes included BSIDII subdomains and perinatal outcomes. Multivariable logistic regression models were performed to control for confounders. RESULTS: Of 557 women undergoing cesarean delivery, 119 (21%) received general anesthesia. There were no differences in the primary composite outcome of developmental delay (aOR 0.93, 95% CI 0.61 to 1.43) or the BSIDII subdomains of mild, moderate, or severe mental delay, or mild or moderate motor delay. Severe motor delay was more common among infants exposed to general anesthesia (aOR 1.98, 95% CI 1.06 to 3.69). Infants exposed to general anesthesia had longer neonatal intensive care stays (51 vs 37 days, P=0.010). CONCLUSIONS: General anesthesia for cesarean delivery was not associated with overall neurodevelopmental delay at two years of age, except for greater odds of severe motor delay. Future studies should evaluate this finding, as well as the impact on neurodevelopment of longer or multiple anesthetic exposures across all gestational ages.

Phenotypic expansion in Zhu-Tokita-Takenouchi-Kim syndrome caused by de novo variants in the SON gene.

BACKGROUND: The genetic etiology of intellectual and psychomotor disability without a defined spectrum of dysmorphic features is usually monogenic. As no diagnostic criteria for such diseases are established, the clinical diagnosis becomes to be a challenge. The object of our paper is to present two patients with non-specific clinical symptoms for whom whole-exome-sequencing identified the new SON mutations and thus allowed for establishing the diagnosis of Zhu-Tokita-Takenouchi-Kim (ZTTK) syndrome. In both patients, the same symptoms including hypotonia, developmental and speech delay, feeding difficulties as well as frequent infections of the respiratory tract and internal ear were observed. However, both cases presented also with exceptional symptoms such as in case 1 ventriculomegaly and asymmetry of ventricles, hypoplastic left heart syndrome (HLHS), intellectual disability, intestinal malrotation, gastroparesis, and duodenal atresia and in the case 2 febrile seizures and reduced IgA levels. We will be presenting the patients and comparing them to 30 previously described cases. METHODS: Whole-exome sequencing (WES) was performed on the probands' DNA and paired-end sequenced (2x100 bp) on HiSeq 1500. Variants considered as disease-causing were validated in the proband and studied in all available family members by amplicon deep sequencing performed using Nextera XT Kit and sequenced on HiSeq 1500. RESULTS: We have identified two new variants in SON gene. In case 1 it has been a heterozygous frameshift variant p.(Ala1340GlnfsTer26), while in case 2 it has been a heterozygous frameshift variant, p.(Asp1640GlyfsTer7). Both variants are described for the first time and up to now, are not mentioned in any database. CONCLUSION: As there are no precise criteria established for the clinical diagnosis of ZTTK, an identification of SON gene mutation by whole-exome-sequencing is the best method that allows for a diagnosis of this syndrome.

Identification of Two Novel Mutations in COG5 Causing Congenital Disorder of Glycosylation.

OBJECTIVE: This study reports a Chinese patient with a Congenital Disorder of Glycosylation (CDG) caused by compound-heterozygous mutations in the Conserved Oligomeric Golgi 5 (COG5) gene and thereby offers concrete evidence for early diagnosis. METHODS: The clinical manifestations, the results of laboratory examinations and genetic analysis of a 4-year-old Chinese girl with CDG are reported. We also reviewed previous CDG cases that involved COG5 mutations by comparing the phenotypes and genotypes in different cases. RESULTS: The patient was admitted to our hospital due to ataxia and psychomotor delay. The major clinical manifestations were postural instability, difficulty in walking, psychomotor delay, hypohidrosis, hyperkeratosis of the skin, and ulnar deviation of the right-hand fingers. Biochemical analyses revealed coagulation defect and liver lesions. Vision tests showed choroidopathy and macular hypoplasia. Whole-exome sequencing identified the hitherto unreported compound-heterozygous COG5 mutations, c.1290C > A (p.Y430X) and c.2077A > C (p.T693P). Mutation p.Y430X is nonsense, leading to a truncated protein. Mutation p.T693P is located at a highly conserved region, and thus the polar-to-non-polar substitution presumably affects the structure and function of COG5. According to the Human Genome Mutation Database Professional, there have been totally 13 CDG cases caused by 13 COG5 mutations. They are mainly characterized by psychomotor delay, hypotonia, ataxia, microcephaly, and hearing and visual abnormalities. CONCLUSION: The clinical manifestations of the patient are mild but consistent with the clinical characteristics of the published COG5-CDG cases. The results of this study extend the spectrum of clinical and genetic findings in COG5-CDG.

Long-term observation of a Japanese mucolipidosis IV patient with a novel homozygous p.F313del variant of MCOLN1.

Mucolipidosis type IV (MLIV) is an autosomal recessively inherited lysosomal storage disorder characterized by progressive psychomotor delay and retinal degeneration that is associated with biallelic variants in the MCOLN1 gene. The gene, which is expressed in late endosomes and lysosomes of various tissue cells, encodes the transient receptor potential channel mucolipin 1 consisting of six transmembrane domains. Here, we described 14-year follow-up observation of a 4-year-old Japanese male MLIV patient with a novel homozygous in-frame deletion variant p.(F313del), which was identified by whole-exome sequencing analysis. Neurological examination revealed progressive psychomotor delay, and atrophy of the corpus callosum and cerebellum was observed on brain magnetic resonance images. Ophthalmologically, corneal clouding has remained unchanged during the follow-up period, whereas optic nerve pallor and retinal degenerative changes exhibited progressive disease courses. Light-adapted electroretinography was non-recordable. Transmission electron microscopy of granulocytes revealed characteristic concentric multiple lamellar structures and an electron-dense inclusion in lysosomes. The in-frame deletion variant was located within the second transmembrane domain, which is of putative functional importance for channel properties.

ATP8A2-related disorders as recessive cerebellar ataxia.

ATP8A2-related disorders are autosomal recessive conditions that associate encephalopathy with or without hypotonia, psychomotor delay, abnormal movements, chorea, tremor, optic atrophy and cerebellar atrophy (CARMQ4). Through a multi-centric collaboration, we identified six point mutations (one splice site and five missense mutations) involving ATP8A2 in six individuals from five families. Two patients from one family with the homozygous p.Gly585Val mutation had a milder presentation without encephalopathy. Expression and functional studies of the missense mutations demonstrated that protein levels of four of the five missense variants were very low and lacked phosphatidylserine-activated ATPase activity. One variant p.Ile215Leu, however, expressed at normal levels and displayed phospholipid-activated ATPase activity similar to the non-mutated protein. We therefore expand for the first time the phenotype related to ATP8A2 mutations to less severe forms characterized by cerebellar ataxia without encephalopathy and suggest that ATP8A2 should be analyzed for all cases of syndromic or non-syndromic recessive or sporadic ataxia.

A novel variant m.8561C>T in the overlapping region of MT-ATP6 and MT-ATP8 in a child with early-onset severe neurological signs.

Among mitochondrial diseases, isolated complex V (CV) deficiency represents a rare cause of respiratory chain (RC) dysfunction. In mammalian mitochondrial DNA (mtDNA), MT-ATP6 partly overlaps with MT-ATP8 making double mutations possible, yet extremely rarely reported principally in patients with cardiomyopathy. Here, we report a novel m.8561 C>T substitution in the overlapping region of MT-ATP6 and MT-ATP8 in a child with early-onset ataxia, psychomotor delay and microcephaly, enlarging the clinical manifestations spectrum associated with CV deficiency.

Precocious and Early Central Puberty in Children With Pre-existing Medical Conditions: A Single Center Study.

Background: Precocious and early puberty are reported findings in children with pre-existing medical conditions including certain syndromes. Series pertaining to such situations are limited. Methods: A retrospective, single-center study was conducted on children with central precocious puberty (onset before the age of 8 years in girls and 9 years in boys) or early puberty (onset between 8 and 9 years in girls and between 9 and 10.5 years in boys) diagnosed on the background of a known pre-existing chronic significant medical condition. Patients with a CNS tumor and those exposed to cranial irradiation were excluded. Results: Precocious puberty was diagnosed in 13 patients and early puberty in 12. Mean age at onset of puberty was 6.65 ± 2.3 years in girls (n = 15) and 9.4 ± 0.84 years in boys (n = 10). The most common disorders were psychomotor delay (n = 12), psychiatric disorders (n = 7) and/or epilepsy (n = 5). Precocious or early puberty was among the symptoms experienced by patients with a variety of syndromes including lipofuscinosis (2 siblings), Dravet syndrome and Silver-Russel syndrome. Pituitary stalk interruption with agenesis of olfactory bulbs and optic nerve atrophy was found on imaging in one patient who presented with blindness, epilepsy, and autism spectrum disorder. The other diseases associated with precocious or early puberty are adrenocorticotropic deficiency, dyspraxia and bone abnormalities, glomerulopathy with complete renal failure, and repeated intra-fetal deaths in the mother. Karyotype analysis revealed chromosomal duplication (chromosome 15 in 2 cases; chromosomes 17 and 11 in one case each) in 4 of 8 patients evaluated. Conclusions: Data from patients with complex disease who experience precocious or early puberty may provide clues regarding the genetic determinants of pubertal development.

Clinical heterogeneity of glycine encephalopathy in three Palestinian siblings: A novel mutation in the glycine decarboxylase (GLDC) gene.

INTRODUCTION: Glycine encephalopathy (GE), also known as non-ketotic hyperglycinemia (NKH), is a rare inborn error of glycine metabolism caused by a defect in glycine cleavage system, a multi-enzyme complex located in mitochondrial membrane. This defect results in elevated glycine concentration in plasma and cerebrospinal fluid (CSF). Clinical manifestations vary from severe lethargy, hypoactivity and apneic episodes in the neonatal form, mild or moderate psychomotor delay and seizures in the infantile form, and abnormal behaviors, ataxia and choreoathetoid movements in late onset form. More than 50 GLDC mutations were found, reflecting large heterogeneity of the gene. METHODS: We describe the clinical, biochemical and molecular characteristics of three Palestinian siblings who have distinct clinical phenotypes. Molecular study was performed utilizing standard Polymerase Chain Reaction (PCR) amplification then direct DNA sequencing for the affected family members. RESULTS: Their phenotypes included severe symptoms in neonatal period, infantile onset of seizure and psychomotor delay and a mild late-onset form with speech delay at age 20months. All siblings were homozygous for a novel mutation Y164H in exon 4 of GLDC gene. The described novel homozygous variant in our study is predicted deleterious and pathogenic. CONCLUSIONS: This article further expands the genetic spectrum of glycine encephalopathy and adds an evidence of the clinical heterogeneity of glycine encephalopathy even in siblings with identical mutation.

Double Interstitial Deletion of the Long Arm of Chromosome 6 in a Patient with Pierre Robin Sequence, Dysmorphisms, and Severe Developmental Delay.

Reported here is the case of a 1.8-year-old boy with a 9.6- Mb deletion in 6q13q14.1 and an 11.2-Mb deletion in 6q21q22.31, ascertained through array CGH, as the result of a complex de novo chromosome rearrangement. The clinical picture of this patient is characterized by severe psychomotor delay, dysmorphic features, and some congenital defects. Although, as reported in the literature, phenotypes associated with 6q deletions may vary, an attempt was made to associate the patient's symptoms to either deletion, comparing them to previously reported cases. Only a limited specific correlation was found, probably due to the prevalence of very common symptoms.

Is cutis verticis Gyrata-Intellectual Disability syndrome an underdiagnosed condition? A case report and review of 62 cases.

Cutis Verticis Gyrata-Intellectual Disability (CVG-ID) syndrome is a rare neurocutaneous syndrome characterized by intellectual disability and scalp folds and furrows that are typically absent at birth and are first noticed after puberty. First reported in 1893, the syndrome was mainly identified in subjects living in psychiatric institutions, where it was found to have a prevalence of up to 11.4%. Most patients were reported in the literature during the first half of the 20th century. CVG-ID is now a less reported and possibly under-recognized syndrome. Here, we report a patient with CVG-ID that was diagnosed using the novel approach of magnetic resonance imaging and we conduct a systematic review of all patients reported in the last 60 years, discussing the core clinical features of this syndrome. © 2016 Wiley Periodicals, Inc.

Novel mutations in KARS cause hypertrophic cardiomyopathy and combined mitochondrial respiratory chain defect.

Mutations in KARS, which encodes for both mitochondrial and cytoplasmic lysyl-tRNA synthetase, have been so far associated with three different phenotypes: the recessive form of Charcot-Mary-Tooth polyneuropathy, the autosomal recessive nonsyndromic hearing loss and the last recently described condition related to congenital visual impairment and progressive microcephaly. Here we report the case of a 14-year-old girl with severe cardiomyopathy associated to mild psychomotor delay and mild myopathy; moreover, a diffuse reduction of cytochrome C oxidase (COX, complex IV) and a combined enzymatic defect of complex I (CI) and complex IV (CIV) was evident in muscle biopsy. Using the TruSight One sequencing panel we identified two novel mutations in KARS. Both mutations, never reported previously, occur in a highly conserved region of the catalytic domain and displayed a dramatic effect on KARS stability. Structural analysis confirmed the pathogenic role of the identified variants. Our findings confirm and emphasize that mt-aminoacyl-tRNA synthetases (mt-ARSs) enzymes are related to a broad clinical spectrum due to their multiple and still unknown functions.