Sex influences clinical phenotype in valosin-containing protein mutations: A case family report and systematic literature review.

OBJECTIVE: Mutations in the valosin-containing protein (VCP) gene cause autosomal dominant multisystem proteinopathy 1 (MSP1), characterized by a variable combination of inclusion body myopathy (IBM), Paget's disease of bone (PDB), and frontotemporal dementia (FTD). Here we report a novel VCP missense mutations in an Italian family with FTD as the prevalent manifestation and compare our results with those described in the literature. METHODS: We described the clinical, molecular, and imaging data of the studied family. We also conducted a systematic literature search with the aim of comparing our findings with previously reported VCP-related phenotypes. RESULTS: A novel heterozygous VCP missense mutation (c 0.473 T > C/p.Met158Thr) was found in all the affected family members. The proband is a 69-year-old man affected by progressive muscle weakness since the age of 49. Muscle MRI showed patchy fatty infiltration in most muscles, and STIR sequences revealed an unusual signal increase in distal leg muscles. At age 65, he presented a cognitive disorder suggestive of behavioral variant FTD. A bone scintigraphy also revealed PDB. The patient's mother, his maternal aunt and her daughter had died following a history of cognitive deterioration consistent with FTD; the mother also had PDB. No relatives had any muscular impairments. Reviewing the literature data, we observed a different sex distribution of VCP-related phenotypes, being FTD prevalence higher among women as compared to men (51.2 % vs 31.2 %) and IBM prevalence higher among men as compared to women (92.1 % vs 72.8 %). DISCUSSION: This study broadened our clinical, genetic, and imaging knowledge of VCP-related disorders.

Using Cluster Analysis to Overcome the Limits of Traditional Phenotype-Genotype Correlations: The Example of RYR1-Related Myopathies.

Thanks to advances in gene sequencing, RYR1-related myopathy (RYR1-RM) is now known to manifest itself in vastly heterogeneous forms, whose clinical interpretation is, therefore, highly challenging. We set out to develop a novel unsupervised cluster analysis method in a large patient population. The objective was to analyze the main RYR1-related characteristics to identify distinctive features of RYR1-RM and, thus, offer more precise genotype-phenotype correlations in a group of potentially life-threatening disorders. We studied 600 patients presenting with a suspicion of inherited myopathy, who were investigated using next-generation sequencing. Among them, 73 index cases harbored variants in RYR1. In an attempt to group genetic variants and fully exploit information derived from genetic, morphological, and clinical datasets, we performed unsupervised cluster analysis in 64 probands carrying monoallelic variants. Most of the 73 patients with positive molecular diagnoses were clinically asymptomatic or pauci-symptomatic. Multimodal integration of clinical and histological data, performed using a non-metric multi-dimensional scaling analysis with k-means clustering, grouped the 64 patients into 4 clusters with distinctive patterns of clinical and morphological findings. In addressing the need for more specific genotype-phenotype correlations, we found clustering to overcome the limits of the "single-dimension" paradigm traditionally used to describe genotype-phenotype relationships.

A Schematic Approach to Defining the Prevalence of COL VI Variants in Five Years of Next-Generation Sequencing.

OBJECTIVE: To define the prevalence of variants in collagen VI genes through a next-generation sequencing (NGS) approach in undiagnosed patients with suspected neuromuscular disease and to propose a diagnostic flowchart to assess the real pathogenicity of those variants. METHODS: In the past five years, we have collected clinical and molecular information on 512 patients with neuromuscular symptoms referred to our center. To pinpoint variants in COLVI genes and corroborate their real pathogenicity, we sketched a multistep flowchart, taking into consideration the bioinformatic weight of the gene variants, their correlation with clinical manifestations and possible effects on protein stability and expression. RESULTS: In Step I, we identified variants in COLVI-related genes in 48 patients, of which three were homozygous variants (Group 1). Then, we sorted variants according to their CADD score, clinical data and complementary studies (such as muscle and skin biopsy, study of expression of COLVI on fibroblast or muscle and muscle magnetic resonance). We finally assessed how potentially pathogenic variants (two biallelic and 12 monoallelic) destabilize COL6A1-A2-A3 subunits. Overall, 15 out of 512 patients were prioritized according to this pipeline. In seven of them, we confirmed reduced or absent immunocytochemical expression of collagen VI in cultured skin fibroblasts or in muscle tissue. CONCLUSIONS: In a real-world diagnostic scenario applied to heterogeneous neuromuscular conditions, a multistep integration of clinical and molecular data allowed the identification of about 3% of those patients harboring pathogenetic collagen VI variants.

Expanding the clinical-pathological and genetic spectrum of RYR1-related congenital myopathies with cores and minicores: an Italian population study.

Mutations in the RYR1 gene, encoding ryanodine receptor 1 (RyR1), are a well-known cause of Central Core Disease (CCD) and Multi-minicore Disease (MmD). We screened a cohort of 153 patients carrying an histopathological diagnosis of core myopathy (cores and minicores) for RYR1 mutation. At least one RYR1 mutation was identified in 69 of them and these patients were further studied. Clinical and histopathological features were collected. Clinical phenotype was highly heterogeneous ranging from asymptomatic or paucisymptomatic hyperCKemia to severe muscle weakness and skeletal deformity with loss of ambulation. Sixty-eight RYR1 mutations, generally missense, were identified, of which 16 were novel. The combined analysis of the clinical presentation, disease progression and the structural bioinformatic analyses of RYR1 allowed to associate some phenotypes to mutations in specific domains. In addition, this study highlighted the structural bioinformatics potential in the prediction of the pathogenicity of RYR1 mutations. Further improvement in the comprehension of genotype-phenotype relationship of core myopathies can be expected in the next future: the actual lack of the human RyR1 crystal structure paired with the presence of large intrinsically disordered regions in RyR1, and the frequent presence of more than one RYR1 mutation in core myopathy patients, require designing novel investigation strategies to completely address RyR1 mutation effect.

Expanding the clinical and genetic spectrum of pathogenic variants in STIM1.

INTRODUCTION/AIMS: Stromal interaction molecule 1 (STIM1) is a reticular Ca2+ sensor composed of a luminal and a cytosolic domain. Autosomal dominant mutations in STIM1 cause tubular aggregate myopathy and Stormorken syndrome or its variant York platelet syndrome. In this study we aimed to expand the features related to new variants in STIM1. METHODS: We performed a cross-sectional study of individuals harboring monoallelic STIM1 variants recruited at five tertiary centers involved in a study of inherited myopathies analyzed with a multigene-targeted panel. RESULTS: We identified seven individuals (age range, 26-57 years) harboring variants in STIM1, including five novel changes: three located in the EF-hand domain, one in the sterile α motif (SAM) domain, and one in the cytoplasmatic region of the protein. Functional evaluation of the pathogenic variants using a heterologous expression system and measuring store-operated calcium entry demonstrated their causative role and suggested a link of new variants with the clinical phenotype. Muscle contractures, found in three individuals, showed variability in body distribution and in the number of joints involved. Three patients showed cardiac and respiratory involvement. Short stature, hyposplenism, sensorineural hearing loss, hypothyroidism, and Gilbert syndrome were variably observed among the patients. Laboratory tests revealed hyperCKemia in six patients, thrombocytopenia in two patients, and hypocalcemia in one patient. Muscle biopsy showed the presence of tubular aggregates in three patients, type I fiber atrophy in one patient, and nonspecific myopathic changes in two patients. DISCUSSION: Our clinical, histological, and molecular data expand the genetic and clinical spectrum of STIM1-related diseases.

The Diagnostic Approach to Mitochondrial Disorders in Children in the Era of Next-Generation Sequencing: A 4-Year Cohort Study.

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.

Early Findings in Neonatal Cases of RYR1-Related Congenital Myopathies.

Ryanodine receptor type 1-related congenital myopathies are the most represented subgroup among congenital myopathies (CMs), typically presenting a central core or multiminicore muscle histopathology and high clinical heterogeneity. We evaluated a cohort of patients affected with Ryanodine receptor type 1-related congenital myopathy (RYR1-RCM), focusing on four patients who showed a severe congenital phenotype and underwent a comprehensive characterization at few months of life. To date there are few reports on precocious instrumental assessment. In two out of the four patients, a muscle biopsy was performed in the first days of life (day 5 and 37, respectively) and electron microscopy was carried out in two patients detecting typical features of congenital myopathy. Two patients underwent brain MRI in the first months of life (15 days and 2 months, respectively), one also a fetal brain MRI. In three children electromyography was performed in the first week of life and neurogenic signs were excluded. Muscle MRI obtained within the first years of life showed a typical pattern of RYR1-CM. The diagnosis was confirmed through genetic analysis in three out of four cases using Next Generation Sequencing (NGS) panels. The development of a correct and rapid diagnosis is a priority and may lead to prompt medical management and helps optimize inclusion in future clinical trials.

Protein aggregates and autophagy involvement in a family with a mutation in Z-band alternatively spliced PDZ-motif protein.

Z-band alternatively spliced PDZ-motif protein (ZASP) is a sarcomeric component expressed both in cardiac and skeletal muscles. Mutations in the LDB3/ZASP gene cause cardiomyopathy and myofibrillar myopathy. We describe a c.76C>T / p.[Pro26Ser] mutation in the PDZ motif of LDB3/ZASP in two siblings exhibiting late-onset myopathy with axial, proximal and distal muscles involvement and marked variability in clinical severity in the absence of a significant family history for neuromuscular disorders. Notably, we identified involvement of the psoas muscle on MRI and muscle CT, a feature not previously documented. Proband's muscle biopsy showed an increase of ZASP expression by western blotting. Muscle fibres morphological features included peculiar sarcolemmal invaginations, pathological aggregates positive to ZASP, ubiquitin, p62 and LC3 antibodies, and the accumulation of autophagic vacuoles, suggesting that protein aggregate formation and autophagy are involved in this additional case of zaspopathy.

Evaluation of Chromosome Microarray Analysis in a Large Cohort of Females with Autism Spectrum Disorders: A Single Center Italian Study.

Autism spectrum disorders (ASD) encompass a heterogeneous group of neurodevelopmental disorders resulting from the complex interaction between genetic and environmental factors. Thanks to the chromosome microarray analysis (CMA) in clinical practice, the accurate identification and characterization of submicroscopic deletions/duplications (copy number variants, CNVs) associated with ASD was made possible. However, the widely acknowledged excess of males on the autism spectrum reflects on a paucity of CMA studies specifically focused on females with ASD (f-ASD). In this framework, we aim to evaluate the frequency of causative CNVs in a single-center cohort of idiopathic f-ASD. Among the 90 f-ASD analyzed, we found 20 patients with one or two potentially pathogenic CNVs, including those previously associated with ASD (located at 16p13.2 16p11.2, 15q11.2, and 22q11.21 regions). An exploratory genotype/phenotype analysis revealed that the f-ASD with causative CNVs had statistically significantly lower restrictive and repetitive behaviors than those without CNVs or with non-causative CNVs. Future work should focus on further understanding of f-ASD genetic underpinnings, taking advantage of next-generation sequencing technologies, with the ultimate goal of contributing to precision medicine in ASD.

Respiratory muscle involvement in HNRNPDL LGMD D3 muscular dystrophy: an extensive clinical description of the first Italian patient.

Limb girdle muscular dystrophy is a genetically inherited condition that primarily affects skeletal muscle leading to progressive, predominantly proximal muscle weakness at presentation. Autosomal dominant LGMD represent 10% of all LGMDs. HNRNPDL-related muscular dystrophy, LGMD1G/LGMD D3 (MIM#609115), is an extremely rare autosomal dominant adult onset myopathy described in a handful of families. Here we fully characterized the muscular and respiratory involvement of a 58 years old Italian woman presenting the previously reported pathogenic variant c.1132G > C p.(Asp378Asn) in the HNRNPDL gene.

MYH2 myopathy, a new case expands the clinical and pathological spectrum of the recessive form.

BACKGROUND: Hereditary myosin myopathies are a group of rare muscle disorders, caused by mutations in genes encoding for skeletal myosin heavy chains (MyHCs). MyHCIIa is encoded by MYH2 and is expressed in fast type 2A and 2B muscle fibers. MYH2 mutations are responsible for an autosomal dominant (AD) progressive myopathy, characterized by the presence of rimmed vacuoles and by a reduction in the number and size of type 2A fibers, and a recessive early onset myopathy characterized by complete loss of type 2A fibers. Recently, a patient with a homozygous mutation but presenting a dominant phenotype has been reported. METHODS: The patient was examined thoroughly and two muscle biopsies were performed through the years. NGS followed by confirmation in Sanger sequencing was used to identify the genetic cause. RESULTS: We describe the second case presenting with late-onset ophthalmoparesis, ptosis, diffuse muscle weakness, and histopathological features typical for AD forms but with a recessive MYH2 genotype. CONCLUSION: This report contributes to expand the clinical and genetic spectrum of MYH2 myopathies and to increase the awareness of these very rare diseases.

Alpha-sarcoglycanopathy presenting as myalgia and hyperCKemia in two adults with a long-term follow-up. Case reports.

Two patients with a paucisymptomatic hyperckemia underwent a skeletal muscle biopsy and massive gene panel to investigate mutations associated with inherited muscle disorders. In the SGCA gene, sequence analyses revealed a homozygous c.850C > T/p.Arg284Cys in patient 1 and two heterozygous variants (c.739G > A/p.Val247Met and c.850C > T/p.Arg284Cys) in patient 2. Combination of histology and immunofluorence studies showed minimal changes for muscular proteins including the α-sarcoglycan. These two cases highlight the advantages of next-generation sequencing in the differential diagnosis of mild myopathic conditions before considering the more invasive muscle biopsy in sarcoglycanopathies.

Next-generation sequencing approach to hyperCKemia: A 2-year cohort study.

OBJECTIVE: Next-generation sequencing (NGS) was applied in molecularly undiagnosed asymptomatic or paucisymptomatic hyperCKemia to investigate whether this technique might allow detection of the genetic basis of the condition. METHODS: Sixty-six patients with undiagnosed asymptomatic or paucisymptomatic hyperCKemia, referred to tertiary neuromuscular centers over an approximately 2-year period, were analyzed using a customized, targeted sequencing panel able to investigate the coding exons and flanking intronic regions of 78 genes associated with limb-girdle muscular dystrophies, rhabdomyolysis, and metabolic and distal myopathies. RESULTS: A molecular diagnosis was reached in 33 cases, corresponding to a positive diagnostic yield of 50%. Variants of unknown significance were found in 17 patients (26%), whereas 16 cases (24%) remained molecularly undefined. The major features of the diagnosed cases were mild proximal muscle weakness (found in 27%) and myalgia (in 24%). Fourteen patients with a molecular diagnosis and mild myopathic features on muscle biopsy remained asymptomatic at a 24-month follow-up. CONCLUSIONS: This study of patients with undiagnosed hyperCKemia, highlighting the advantages of NGS used as a first-tier diagnostic approach in genetically heterogeneous conditions, illustrates the ongoing evolution of molecular diagnosis in the field of clinical neurology. Isolated hyperCKemia can be the sole feature alerting to a progressive muscular disorder requiring careful surveillance.

VARS2-linked mitochondrial encephalopathy: two case reports enlarging the clinical phenotype.

BACKGROUND: Mitochondrial respiratory chain consists of five complexes encoded by nuclear and mitochondrial genomes. Mitochondrial aminoacyl-tRNA synthetases are key enzymes in the synthesis of such complexes. Bi-allelic variants of VARS2, a nuclear gene encoding for valyl-tRNA (Val-tRNA) synthetase, are associated to several forms of mitochondrial encephalopathies or cardiomyoencephalopathies. Among these, the rare homozygous c.1100C > T (p.Thr367Ile) mutation variably presents with progressive developmental delay, axial hypotonia, limbs spasticity, drug-resistant epilepsy leading, in some cases, to premature death. Yet only six cases, of which three are siblings, harbouring this homozygous mutation have been described worldwide. CASE PRESENTATION: Hereby, we report two additional cases of two non-related young girls from Sardinia, born from non-consanguineous and healthy parents, carrying the aforesaid homozygous VARS2 variant. At onset both the patients presented with worsening psychomotor delay, muscle hypotonia and brisk tendon reflexes. Standard genetic tests were normal, as well as metabolic investigations. Brain MRI showed unspecific progressive abnormalities, such as corpus callosum hypoplasia (patient A) and cerebellar atrophy (patient A and B). Diagnosis was reached by adopting massive parallel next generation sequencing. Notably clinical phenotype of the first patient appears to be milder compared to previous known cases. The second patient eventually developed refractory epilepsy and currently presents with severe global impairment. Because no specific treatment is available as yet, both patients are treated with supporting antioxidant compounds along with symptomatic therapies. CONCLUSIONS: Given the paucity of clinical data about this very rare mitochondrial encephalopathy, our report might contribute to broaden the phenotypic spectrum of the disorder. Moreover, noteworthy, three out of five pedigrees so far described belong to the Northern Sardinia ethnicity.

Complex multisystem phenotype associated with the mitochondrial DNA m.5522G>A mutation.

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.

Broad phenotypic spectrum and genotype-phenotype correlations in GMPPB-related dystroglycanopathies: an Italian cross-sectional study.

BACKGROUND: Dystroglycanopathy (α-DG) is a relatively common, clinically and genetically heterogeneous category of congenital forms of muscular dystrophy (CMD) and limb-girdle muscular dystrophy (LGMD) associated with hypoglycosylated α-dystroglycan. To date, mutations in at least 19 genes have been associated with α-DG. One of them, GMPPB, encoding the guanosine-diphosphate-mannose (GDP-mannose) pyrophosphorylase B protein, has recently been associated with a wide clinical spectrum ranging from severe Walker-Warburg syndrome to pseudo-metabolic myopathy and even congenital myasthenic syndromes. We re-sequenced the full set of known disease genes in 73 Italian patients with evidence of either reduced or nearly absent α-dystroglycan to assess genotype-phenotype correlations in this cohort. We used innovative bioinformatic tools to calculate the effects of all described GMPPB mutations on protein function and attempted to correlate them with phenotypic expressions. RESULTS: We identified 13 additional cases from 12 families and defined seven novel mutations. Patients displayed variable phenotypes including less typical pictures, ranging from asymptomatic hyperCKemia, to arthrogryposis and congenital clubfoot at birth, and also showed neurodevelopmental comorbidities, such as seizures and ataxic gait, as well as autism-spectrum disorder, which is seldom described in clinical reports of dystroglycanopathies. We also demonstrated that few mutations recur in the Italian GMPPB-mutated population and that alterations of protein stability are the main effects of GMPPB missense variants. CONCLUSION: This work adds to the data on genotype-phenotype correlations in α-DG and offers new bionformatic tools to provide the conceptual framework needed to understand the complexity of these disorders.

Congenital myopathies: clinical phenotypes and new diagnostic tools.

Congenital myopathies are a group of genetic muscle disorders characterized clinically by hypotonia and weakness, usually from birth, and a static or slowly progressive clinical course. Historically, congenital myopathies have been classified on the basis of major morphological features seen on muscle biopsy. However, different genes have now been identified as associated with the various phenotypic and histological expressions of these disorders, and in recent years, because of their unexpectedly wide genetic and clinical heterogeneity, next-generation sequencing has increasingly been used for their diagnosis. We reviewed clinical and genetic forms of congenital myopathy and defined possible strategies to improve cost-effectiveness in histological and imaging diagnosis.

Neutral Lipid Storage Diseases: clinical/genetic features and natural history in a large cohort of Italian patients.

BACKGROUND: A small number of patients affected by Neutral Lipid Storage Diseases (NLSDs: NLSD type M with Myopathy and NLSD type I with Ichthyosis) have been described in various ethnic groups worldwide. However, relatively little is known about the progression and phenotypic variability of the disease in large specific populations. The aim of our study was to assess the natural history, disability and genotype-phenotype correlations in Italian patients with NLSDs. Twenty-one patients who satisfied the criteria for NLSDs were enrolled in a retrospective cross-sectional study to evaluate the genetic aspects, clinical signs at onset, disability progression and comorbidities associated with this group of diseases. RESULTS: During the clinical follow-up (range: 2-44 years, median: 17.8 years), two patients (9.5%, both with NLSD-I) died of hepatic failure, and a further five (24%) lost their ability to walk or needed help when walking after a mean period of 30.6 years of disease. None of the patients required mechanical ventilation. No patient required a heart transplant, one patient with NLSD-M was implanted with a cardioverter defibrillator for severe arrhythmias. CONCLUSION: The genotype/phenotype correlation analysis in our population showed that the same gene mutations were associated with a varying clinical onset and course. This study highlights peculiar aspects of Italian NLSD patients that differ from those observed in Japanese patients, who were found to be affected by a marked hypertrophic cardiopathy. Owing to the varying phenotypic expression of the same mutations, it is conceivable that some additional genetic or epigenetic factors affect the symptoms and progression in this group of diseases.

Late onset of neutral lipid storage disease due to novel PNPLA2 mutations causing total loss of lipase activity in a patient with myopathy and slight cardiac involvement.

Neutral lipid storage disease with myopathy (NLSDM) presents with skeletal muscle myopathy and severe dilated cardiomyopathy in nearly 40% of cases. NLSDM is caused by mutations in the PNPLA2 gene, which encodes the adipose triglyceride lipase (ATGL). Here we report clinical and genetic findings of a patient carrying two novel PNPLA2 mutations (c.696+4A>G and c.553_565delGTCCCCCTTCTCG). She presented at age 39 with right upper limb abduction weakness slowly progressing over the years with asymmetric involvement of proximal upper and lower limb muscles. Cardiological evaluation through ECG and heart echo scan was normal until the age 53, when mild left ventricular diastolic dysfunction was detected. Molecular analysis revealed that only one type of PNPLA2 transcript, with exon 5 skipping, was expressed in patient cells. Such aberrant mRNA causes the production of a shorter ATGL protein, lacking part of the catalytic domain. This is an intriguing case, displaying severe PNPLA2 mutations with clinical presentation characterized by slight cardiac impairment and full expression of severe asymmetric myopathy.