Irene Colombo

Optic atrophy plus phenotype due to mutations in the OPA1 gene: two more Italian families.

Autosomal Dominant Optic Atrophy (ADOA) is characterized by the selective degeneration of retinal ganglion cells. The occurrence of mutations in the gene encoding the dynamin-like GTPase protein Optic Atrophy 1 (OPA1) has been observed in about 60–70% of ADOA cases. A subset of missense mutations, mostly within the GTPase domain, has recently been associated with a syndromic ADOA form called “OPA1 plus” phenotype presenting, at muscle level, mitochondrial DNA (mtDNA) instability. In this study we disclosed two OPA1 gene mutations in independent probands from two families affected by OPA1 plus phenotype: the previously reported c.985-2A > G substitution and a novel microdeletion (c.2819-1_2821del). The correlation between genotype and phenotype and the effects of these variants at the transcript level and in the muscle tissue were investigated, confirming the broad complexity in the phenotypic spectrum associated with these OPA1 mutations.

Longitudinal follow-up and muscle MRI pattern of two siblings with polyglucosan body myopathy due to glycogenin-1 mutation

Polyglucosan bodies (PBs) are deposits of amylopectin-like polysaccharides, detected in muscles of patients affected with glycogenoses-like branching enzyme (GBE) and phosphofructokinase deficiencies.1 Recently, mutations in RBCK1 have been associated with a skeletal PBs myopathy,2 as well as mutations in GYG1 , encoding for glycogenyn-1.3 All these conditions have autosomal recessive inheritance. Only seven unrelated cases with mutations in GYG1 have been reported, characterised by variable age at onset (from childhood to 7th decade), mainly proximal weakness, normal creatine kinases (CKs) levels and myopathic electromyography (EMG).3 We have been, for the past 35 years, following two affected sisters now aged 71 and 64 years (P.IV-5 and P.IV-10) (see online supplementary figure S1A). Their parents were both healthy first cousins from a little village in the Italian Alps. Both sisters had normal motor development. At the age of 30 years, P.IV-5 showed weakness in arm abduction, more prominent on the right side. The disease course was slowly progressive over the decades, with early involvement of proximal limb muscles. Waddling gait with hyperlordosis was first observed when she was in her late 40s. She started to use a wheelchair outdoors at the age of 59 years. In the following years she became completely a wheelchair user and dependent for her daily activities. Her last examination, at the age of 71 years, showed facial weakness, which was initially absent, with muscle atrophy and hypotonia, absent deep tendon reflexes (DTR) and severely compromised muscle power (Medical Research Council (MRC) score: neck flexors 3, neck extensors 2, shoulder abductors 0, forearm extensors/flexors 0, wrist extensors 0, wrist flexors and hand grip 2, hip flexors/extensors 0, thigh extensors/flexors 2, foot plantar flexors and …

Steroid-responsive Hashimoto encephalopathy mimicking Creutzfeldt-Jakob disease

Hashimoto’s encephalopathy (HE) is a rare neurological disorder with a heterogeneous group of neurological symptoms associated with high titres of anti-thyroid antibodies. Clinical manifestations may include encephalopathic features such as seizures, behavioural and psychiatric manifestations, movement disorders and coma. The objective of this presentation is to describe a patient with this rare and controversial clinical syndrome mimicking Creutzfeldt–Jakob disease, associated with a Hashimoto euthyroid thyroiditis and with a significant response to high dose intravenous prednisone. The responsiveness of this syndrome to steroids suggests that this disorder involves immune pathogenic mechanisms, as previous reviews reported.

New Mutations in NEB Gene Discovered by Targeted Next-Generation Sequencing in Nemaline Myopathy Italian Patients

Nemaline myopathy represents a group of clinically and genetically heterogeneous neuromuscular disorders. Different clinical-genetic entities have been characterized in the last few years, with implications for diagnostics and genetic counseling. Fifty percent of nemaline myopathy forms are due to NEB mutations, but genetic analysis of this large and complex gene by Sanger sequencing is time consuming and expensive. We selected 10 Italian patients with clinical and biopsy features suggestive for nemaline myopathy and negative for ACTA1, TPM2 and TPM3 mutations. We applied a targeted next-generation sequencing strategy designed to analyse NEB coding regions, the relative full introns and the promoter. We also evaluated copy number variations (by CGH array) and transcriptional changes by RNA Sanger sequencing, whenever possible. This combined strategy revealed 11 likely pathogenic variants in 8 of 10 patients. The molecular diagnosis was fully achieved in 3 of 8 patients, while only one heterozygous mutation was observed in 5 subjects. This approach revealed to be a fast and cost-effective way to analyse the large NEB gene in a small group of patients and might be promising for the detection of pathological variants of other genes featuring large coding regions and lacking mutational hotspots.

Adult Polyglucosan Body Disease: Clinical and histological heterogeneity of a large Italian family

Adult Polyglucosan Body Disease (APBD) is a rare inherited leukodystrophy associated with axonal polyneuropathy, mainly reported in persons of Ashkenazi-Jewish descent. We describe three Italian siblings at disease onset, presenting in their fifties with a combination of pyramidal and ataxic signs, mild demyelinating neuropathy on neurophysiological investigation (1/3 cases) and transient symptoms (1/3). A leucoencephalopathy with infratentorial lesions without enhancement and medullary/spine atrophy was demonstrated on brain/spine MRI (3/3). Muscle biopsy was normal in 2/3; both muscle and nerve biopsy showed polyglucosan bodies in the sibling with polyneuropathy. This indicated a need for GBE1 sequencing, which revealed a novel missense mutation (c.1064G>A; p.Arg355His) and one previously described (c.1604A>G; p.Tyr535Cys) in all siblings. We highlight that peripheral neuropathy, deemed as disease hallmark, may be missing and that transient symptoms are confirmed as early disease manifestations. The pattern of damage at neuro-imaging described recurs irrespective of clinical presentation, constituting a unifying diagnostic clue.

Two novel mutations in PEO1 (Twinkle) gene associated with chronic external ophthalmoplegia

Maintenance and replication of mitochondrial DNA require the concerted action of several factors encoded by nuclear genome. The mitochondrial helicase Twinkle is a key player of replisome machinery. Heterozygous mutations in its coding gene, PEO1, are associated with progressive external ophthalmoplegia (PEO) characterised by ptosis and ophthalmoparesis, with cytochrome c oxidase (COX)-deficient fibres, ragged-red fibres (RRF) and multiple mtDNA deletions in muscle. Here we describe clinical, histological and molecular features of two patients presenting with mitochondrial myopathy associated with PEO. PEO1 sequencing disclosed two novel mutations in exons 1 and 4 of the gene, respectively. Although mutations in PEO1 exon 1 have already been described, this is the first report of mutation occurring in exon 4.

P17 Whole exome sequencing in patients with congenital myopathies

Congenital myopathies (CM) are a group of disorders presenting at birth or early infancy, characterised by muscle weakness and specific changes in the muscle biopsy. During the recent decade a number of genes have been discovered, however, additional novel genes are yet to be identified as genetic diagnosis cannot be currently established in many CM patients. With the aim to identify the genetic defect in 33 CM patients, in whom mutations in suspected genes have been previously excluded, we carried out whole exome sequencing (WES). From the 33 patients, 19 have been resolved and 14 patients are still being investigated as the initial WES data analysis failed to identify possible candidate genes. Among the resolved cases, two patients with muscle biopsy suggestive of core myopathy and one with centronuclear myopathy, carried heterozygous truncating TTN mutations supporting the emerging data that TTN mutations should be investigated as causative in patients with unresolved centronuclear and core myopathy. We also identified a homozygous missense mutation in STAC3 gene in a patient with King-Denborough syndrome and core-like changes on muscle biopsy, indicating a causative role of STAC3 mutations in King–Denborough syndrome. Recently, a homozygous missense mutation in STAC3 gene was identified in patients with Native American myopathy. A patient with a severe phenotype and muscle biopsy changes suggestive of nemaline myopathy, carried a homozygous missense mutation in KLHL40. Mutations in KLHL40 have been very recently identified as a frequent cause of severe autosomal-recessive nemaline myopathy. Ten of the resolved patients carried mutations in potentially causative genes which are currently under investigation.

G.P.261

Congenital myopathies (CM) are a group of disorders presenting at birth or early infancy, characterised by muscle weakness and specific changes in the muscle biopsy. During the recent decade a number of genes have been discovered, however, additional novel genes are yet to be identified as genetic diagnosis cannot be currently established in many CM patients. With the aim to identify the genetic defect in 33 CM patients, in whom mutations in suspected genes have been previously excluded, we carried out whole exome sequencing (WES). From the 33 patients, 19 have been resolved and 14 patients are still being investigated as the initial WES data analysis failed to identify possible candidate genes. Among the resolved cases, two patients with muscle biopsy suggestive of core myopathy and one with centronuclear myopathy, carried heterozygous truncating TTN mutations supporting the emerging data that TTN mutations should be investigated as causative in patients with unresolved centronuclear and core myopathy. We also identified a homozygous missense mutation in STAC3 gene in a patient with King-Denborough syndrome and core-like changes on muscle biopsy, indicating a causative role of STAC3 mutations in King–Denborough syndrome. Recently, a homozygous missense mutation in STAC3 gene was identified in patients with Native American myopathy. A patient with a severe phenotype and muscle biopsy changes suggestive of nemaline myopathy, carried a homozygous missense mutation in KLHL40 . Mutations in KLHL40 have been very recently identified as a frequent cause of severe autosomal-recessive nemaline myopathy. Ten of the resolved patients carried mutations in potentially causative genes which are currently under investigation.

A case report with the peculiar concomitance of 2 different genetic syndromes

Rationale: Down syndrome (DS) is the most common chromosome disorder in live born infants, affecting several body systems, but usually sparing skeletal muscles. We present the case of a child with coexistence of DS and dystrophinopathy. Only 1 similar case has been reported so far. Patient Concerns: An 8-year-old boy with DS had a history of incidental finding of increased serum creatine kinase levels up to 1775 U/L (normal values 38–174 U/L). He presented no delay in motor development; at the neurological examination, no muscle weakness or fatigability was detected in 2 different evaluations performed over a 6-month period. Diagnoses: Skeletal muscle biopsy revealed marked dystrophic changes with patchy immunostaining for dystrophin. The Duchenne muscular dystrophy gene was screened for deletions by multiplex polymerase chain reaction, but no mutations were found. Sequence analysis of the Duchenne muscular dystrophy gene revealed a splice-site mutation c.1812+1G>A in intron 15 and confirmed a diagnosis of Becker muscular dystrophy. Interventions: The patient has started a specific physiotherapy that avoided any deterioration in motor development and muscular wasting. Outcomes: A multidisciplinary follow-up was initiated. The genetician that followed the patient for DS was supported by the neurologist, the physiotherapist, the pulmonologist, and the cardiologist. Lessons: This peculiar “double trouble” case exemplifies the value of careful clinical evaluation and adequate clinical experience to identify the concomitance of 2 different genetic syndromes in the same patient, and it points out the significance of muscular strength assessment in DS patients to make the most correct prognosis, and, consequently, to organize the best long-term care.