Neuromuscular disease genetics in under-represented populations: increasing data diversity.

Neuromuscular diseases (NMDs) affect ∼15 million people globally. In high income settings DNA-based diagnosis has transformed care pathways and led to gene-specific therapies. However, most affected families are in low-to-middle income countries (LMICs) with limited access to DNA-based diagnosis. Most (86%) published genetic data is derived from European ancestry. This marked genetic data inequality hampers understanding of genetic diversity and hinders accurate genetic diagnosis in all income settings. We developed a cloud-based transcontinental partnership to build diverse, deeply-phenotyped and genetically characterized cohorts to improve genetic architecture knowledge, and potentially advance diagnosis and clinical management. We connected 18 centres in Brazil, India, South Africa, Turkey, Zambia, Netherlands and the UK. We co-developed a cloud-based data solution and trained 17 international neurology fellows in clinical genomic data interpretation. Single gene and whole exome data were analysed via a bespoke bioinformatics pipeline and reviewed alongside clinical and phenotypic data in global webinars to inform genetic outcome decisions. We recruited 6001 participants in the first 43 months. Initial genetic analyses 'solved' or 'possibly solved' ∼56% probands overall. In-depth genetic data review of the four commonest clinical categories (limb girdle muscular dystrophy, inherited peripheral neuropathies, congenital myopathy/muscular dystrophies and Duchenne/Becker muscular dystrophy) delivered a ∼59% 'solved' and ∼13% 'possibly solved' outcome. Almost 29% of disease causing variants were novel, increasing diverse pathogenic variant knowledge. Unsolved participants represent a new discovery cohort. The dataset provides a large resource from under-represented populations for genetic and translational research. In conclusion, we established a remote transcontinental partnership to assess genetic architecture of NMDs across diverse populations. It supported DNA-based diagnosis, potentially enabling genetic counselling, care pathways and eligibility for gene-specific trials. Similar virtual partnerships could be adopted by other areas of global genomic neurological practice to reduce genetic data inequality and benefit patients globally.

A novel biallelic frameshift variant in C2orf69 causing developmental regression, seizures, microcephaly, autistic features, and hypertonia.

Combined oxidative phosphorylation deficiency type 53 (COXPD53) is an autosomal recessive neurodevelopmental disorder (NDD) caused by homozygous variants in the gene C2orf69. Here, we report a novel frameshift variant c.187_191dupGCCGA, p.D64Efs*56 identified in an individual with clinical presentation of COXPD53 with developmental regression and autistic features. The variant c.187_191dupGCCGA, p.D64Efs*56 represents the most N-terminal part of C2orf69. Notable clinical features of COXPD53of the proband include developmental delay, developmental regression, seizures, microcephaly, and hypertonia. Structural brain defects of cerebral atrophy, cerebellar atrophy, hypomyelination, and thin corpus callosum were also observed. While we observe strong phenotypic overlap among affected individuals with C2orf69 variants, developmental regression and autistic features have not been previously described in individuals with COXPD53. Together, this case expands the genetic and clinical phenotypic spectrum of C2orf69-associated COXPD53.

Utility of multiparametric pre-operative magnetic resonance imaging in differentiation of chordoid meningioma from the other histopathological subtypes of meningioma-a retrospective study.

PURPOSE: To determine the magnetic resonance imaging (MRI) features which could pre-operatively differentiate chordoid meningioma (CM) from other histopathological subtypes of meningioma. METHODS: Retrospective analysis of pre-operative MRI of cases with histopathologically confirmed diagnosis of meningioma during the last 5 years at our institute was done. T1W, T2W, FLAIR sequences, and post-contrast enhancement were evaluated on a qualitative scale. Normalized ADC ratios (nADCR) and normalized fractional anisotropy ratios (nFAR) were derived. The intratumoral susceptibility score (ITSS), presence of sunburst pattern of vasculature, bone changes, tumour-parenchyma interface, and oedema-to-tumour ratio were also determined. RESULTS: A total of 81 lesions were analyzed out of which 15 were CM. CM showed a higher relative contrast enhancement as compared to all other subtypes except for angiomatous and microcystic meningioma. Relative signal intensity on FLAIR could differentiate CM from transitional meningioma. nFAR was found to be significantly higher in fibroblastic meningioma and significantly lower in microcystic meningiomas as compared to CM. Anaplastic meningiomas were remarkable for bone changes and an ill-defined tumour-brain interface in significantly higher proportion of cases as compared to CM. nADCR > 1.5 was found to be an independent predictor of CM with a sensitivity of 84.6%, specificity of 89.8%, positive predictive value of 64.7%, and negative predictive value of 96.4%. CONCLUSION: Routine pre-operative MRI may be able to differentiate CM from other meningioma subtypes and a cut-off value of greater than 1.5 for nADCR could be predictive of > 50% chordoid histology of meningioma with a high sensitivity, specificity, and negative predictive value.

Exploring immunoreactivity of TTF-1 and AVP in hypothalamic hamartoma.

INTRODUCTION: Hypothalamic hamartoma (HH) is a rare developmental disorder presenting with gelastic seizures or precocious puberty attributed to gonadotrophin-releasing hormone expression by the hamartoma. The histogenesis of HH is uncertain, and diagnosis of HH is difficult in small biopsies due to its close resemblance to normal hypothalamic nuclei. TTF-1 and arginine vasopressin (AVP) are associated with gonadotropin-releasing hormone release. MATERIALS AND METHODS: In this study, we explored the expression pattern of TTF-1 and AVP in HH and its utility, if any, in diagnosis. We reviewed the clinical, radiologic, and histopathological features of 23 HH diagnosed over the past decade at our Institute. RESULTS: The age at presentation ranged from 11 months to 34 years with gelastic seizures (82.6%), precocious puberty (17.4%), and developmental delay (8.7%) as presenting symptoms. On imaging, all the lesions (n = 9) involved the posterior and tuberal group of hypothalamic nuclei, while 5 cases involved the anterior hypothalamus. Anatomically, the lesions involved mammillary body, arcuate and periventricular nuclei. On histopathology, 52% cases revealed nodular arrangement of small neurocytic cells separated by glial stroma. TTF-1 and AVP immunoreactivity was absent in all the cases, whereas in normal hypothalamus, AVP was expressed in periventricular nuclei. CONCLUSION: Our results suggest that immunoexpression of TTF-1 is absent in HH, particularly in those arising from the posterior hypothalamus, and this can be used in small biopsies to distinguish from a normal hypothalamus as well as from posterior pituitary tumors.

A founder mutation in the GMPPB gene [c.1000G > A (p.Asp334Asn)] causes a mild form of limb-girdle muscular dystrophy/congenital myasthenic syndrome (LGMD/CMS) in South Indian patients.

Twelve patients from seven unrelated South Indian families with a limb-girdle muscular dystrophy-congenital myasthenic syndrome (LGMD/CMS) phenotype and recessive inheritance underwent deep clinical phenotyping, electrophysiological evaluation, muscle histopathology, and next-generation sequencing/Sanger sequencing-based identification of the genetic defect. Homozygosity mapping was performed using high-throughput genome-wide genotyping for mapping the mutation and to evaluate the founder effect. The age of disease onset among patients ranged from childhood to 40 years of age. The key clinical manifestations observed were progressive fatigable limb-girdle weakness, muscle hypertrophy/atrophy, and preferential weakness in a dystrophic pattern. The ages at last follow-up ranged from 30 to 64 years; nine were independently ambulant, two required assistance, and one was wheelchair-bound. Lower limb muscle MRI showed varying degrees of fat replacement in the glutei, hamstrings, anterior leg muscles, and medial gastrocnemius. All patients showed significant decrement on repetitive nerve stimulation (RNS). Muscle biopsy in 7 patients revealed varying degrees of dystrophic and neurogenic changes. Treatment with pyridostigmine and/or salbutamol resulted in variable improvement in 10 patients. Genetic analysis showed an identical homozygous GMPPB mutation c.1000G > A (p.Asp334Asn) in all affected patients. A region of homozygosity (6Mbp) was observed flanking the c.1000G > A change in carrier chromosomes. This study identifies c.1000G > A in GMPPB as a common founder mutation in an ethnic community of South Indian descent with milder yet variable degree of clinical presentation of GMPPB-associated LGMD-CMS.

Novel variants broaden the phenotypic spectrum of PLEKHG5-associated neuropathies.

BACKGROUND AND PURPOSE: Pathogenic variants in PLEKHG5 have been reported to date to be causative in three unrelated families with autosomal recessive intermediate Charcot-Marie-Tooth disease (CMT) and in one consanguineous family with spinal muscular atrophy (SMA). PLEKHG5 is known to be expressed in the human peripheral nervous system, and previous studies have shown its function in axon terminal autophagy of synaptic vesicles, lending support to its underlying pathogenetic mechanism. Despite this, there is limited knowledge of the clinical and genetic spectrum of disease. METHODS: We leverage the diagnostic utility of exome and genome sequencing and describe novel biallelic variants in PLEKHG5 in 13 individuals from nine unrelated families originating from four different countries. We compare our phenotypic and genotypic findings with a comprehensive review of cases previously described in the literature. RESULTS: We found that patients presented with variable disease severity at different ages of onset (8-25 years). In our cases, weakness usually started proximally, progressing distally, and can be associated with intermediate slow conduction velocities and minor clinical sensory involvement. We report three novel nonsense and four novel missense pathogenic variants associated with these PLEKHG5-associated neuropathies, which are phenotypically spinal muscular atrophy (SMA) or intermediate Charcot-Marie-Tooth disease. CONCLUSIONS: PLEKHG5-associated neuropathies should be considered as an important differential in non-5q SMAs even in the presence of mild sensory impairment and a candidate causative gene for a wide range of hereditary neuropathies. We present this series of cases to further the understanding of the phenotypic and molecular spectrum of PLEKHG5-associated diseases.

Sellar atypical teratoid rhabdoid tumor in an adult: Clinical and pathological dilemmas.

An atypical teratoid rhabdoid tumor (ATRT) is a pediatric embryonic tumor of the central nervous system and is uncommon in adults. We report a case of a 33-year-old female who presented with multiple dural lesions that were diagnosed as ATRT. She had a past history of endoscopic transnasal transsphenoidal and subsequent transcranial decompression of suprasellar lesion 6 months prior, with a presumptive diagnosis of atypical pituitary adenoma, which on retrospective evaluation was confirmed as sellar ATRT. Adult sellar ATRT, though rare, has now been proposed as a distinct clinicopathological and genetic variant that is predominantly seen in middle-aged women. We discuss the uniqueness of this rare aggressive tumor with reference to the age, location, and the challenges faced in the clinical and pathological diagnosis.

Case of primary dural epithelioid angiosarcoma with review of literature and differential diagnosis.

The central nervous system (CNS) is an uncommon site for primary epithelioid angiosarcoma. We report a case of a 25-year-old male who presented with swelling over the head, headache, and weakness of the right side for 6 months. MRI revealed a heterogeneously intense large left parietal dural-based, extra-axial mass with dural tail infiltrating the brain parenchyma, overlying calvaria along with mass effect and vasogenic edema in the left parietal lobe. The patient underwent complete resection of the tumor with adjuvant radiotherapy. Histology revealed a mitotically active vasoformative neoplasm with epithelioid morphology which was immunoreactive for CD31, ERG, FLI-1, and variably for CK. Based on the histomorphological and immunohistochemical profile, a diagnosis of epithelioid angiosarcoma was rendered. The extreme rarity in this location and the highly malignant nature of this tumor makes the clinical diagnosis and management very challenging. These tumors are often considered as meningiomas on prebiopsy imaging due to dural location and dural tail. Further, the misconception may continue on histological examination if only EMA is utilized, since both meningioma and epithelioid angiosarcoma can be positive. There are only 10 previous reports of meningeal angiosarcoma reported in the literature.

Cerebral small vessel disease with hemorrhagic stroke related to COL4A1 mutation: A case report.

Stroke is a major cause of mortality and morbidity with a wide variety of etiological risk factors. Cerebral small vessel disease (SVD) is an important cause of stroke in the young with several hereditary disorders affecting these small blood vessels. Mutations in the COL4A1 gene (COL4A1) have been shown to be associated with a broad range of disorders including hemorrhagic stroke, myopathy, glaucoma and others. We report a rare case of stroke in an intellectually disabled 18-year-old girl with radiological evidence of basal ganglia microbleeds, periventricular white matter signal changes and porencephalic cyst. Ophthalmic examination revealed bilateral microcornea and Axenfeld-Rieger anomaly. At autopsy there were hemorrhagic lesions at multiple sites within the brain. Histology revealed thickened small-caliber vessels which demonstrated disruption and fragmentation of the basement membrane by collagen type IV alpha 1 immunohistochemistry and by electron microscopy. A missense COL4A1 mutation involving glycine residue was detected in the patient. The present case illustrates the clinicopathological spectrum of COL4A1-related cerebral SVD presenting as hemorrhagic stroke in the young with porencephaly, intellectual disability, and Axenfield-Rieger anomaly and thus adds to the clinical heterogeneity of this genetic disorder.

Intracranial fungal granuloma: a single-institute study of 90 cases over 18 years.

OBJECTIVE: Intracranial fungal granuloma (IFG) remains an uncommon entity. The authors report a single-institute study of 90 cases of IFG, which is the largest study until now. METHODS: In this retrospective study, all cases of IFG surgically treated in the years 2001-2018 were included. Data were obtained from the medical records and the pathology, microbiology, and radiology departments. All relevant clinical data, imaging characteristics, surgical procedure performed, perioperative findings, and follow-up data were recorded from the case files. Telephonic follow-up was also performed for a few patients to find out their current status. RESULTS: A total of 90 cases consisting of 64 males (71.1%) and 26 (28.9%) females were evaluated. The mean patient age was 40.2 years (range 1-79 years). Headache (54 patients) was the most common presenting complaint, followed by visual symptoms (35 patients), fever (21 patients), and others such as limb weakness (13 patients) or seizure (9 patients). Cranial nerve involvement was the most common sign (47 patients), followed by motor deficit (22 patients) and papilledema (7 patients). The mean duration of symptoms before presentation was 6.4 months (range 0.06-48 months). Thirty patients (33.3%) had predisposing factors like diabetes mellitus, tuberculosis, or other immunocompromised status. A pure intracranial location of the IFG was seen in 49 cases (54.4%), whereas rhinocerebral or paranasal sinus involvement was seen in 41 cases (45.6%). Open surgery, that is, craniotomy and decompression, was performed in 55 cases, endoscopic biopsy was done in 30 cases, and stereotactic biopsy was performed in 5 cases. Aspergilloma (43 patients) was the most common fungal mass, followed by zygomycosis (13 patients), chromomycosis (9 patients), cryptococcoma (7 patients), mucormycosis (5 patients), and candida infection (1 patient). In 12 cases, the exact fungal phenotype could not be identified. Follow-up was available for 69/90 patients (76.7%). The mean duration of the follow-up was 37.97 months (range 3-144 months). The mortality rate was 52.2% (36/69 patients) among the patients with available follow-up. CONCLUSIONS: A high index of suspicion for IFG should exist for patients with an immunocompromised status and diabetic patients with rhinocerebral mass lesions. Early diagnosis, aggressive surgical decompression, and a course of promptly initiated antifungal therapy are associated with a better prognosis.

Multiple Neurenteric Cysts along the Spinal Axis of an Infant: A Rare Entity.

A spinal neurenteric cyst is a rare entity. It commonly presents already at 5 weeks of age up to the 6th decade of life. The most common location is the cervical region followed by thoracic and lumbosacral regions. We report a 9-month-old male infant with sudden onset of weakness in both lower limbs. MRI revealed 2 cystic lesions at cervical and thoracic level with spinal cord compression. He underwent laminectomy and excision of the cervical lesion. The child improved significantly. The postoperative MRI shows complete excision of a dorsal lesion and presence of a cervical lesion. Later, he underwent cervical laminotomy and partial wall excision followed by shunt placement. The histopathological report revealed a neurenteric cyst. Two neurenteric cysts presented in the neuroaxis of the same patient: one was located ventral (thoracic) and the other dorsal (cervical). At the 2-year follow-up, the child was active and walking without support. Multiple cystic lesions in the neuroaxis can be neurenteric cysts.

Surgical Management and Outcome of a Bilateral Thalamic Pilocytic Astrocytoma: Case Report and Review of the Literature.

The incidence of bilateral thalamic glioma in children is not reported in the literature. The majority of cases comprise either diffuse astrocytoma, anaplastic astrocytoma, or glioblastoma. Partial surgical resection or biopsy followed by adjuvant therapy is the usual treatment for bilateral thalamic gliomas. Prognosis is dependent on tumor grade and extent of tumor spread to surrounding critical structures. We present a rare case of bilateral thalamic pilocytic astrocytoma. Endoscopic biopsy, septostomy, and placement of a ventriculoperitoneal shunt was done followed by radiotherapy. The 36-month follow-up demonstrated radiological control of the tumor.

Spinal Intramedullary Ganglioglioma in Children: An Unusual Location of a Common Pediatric Tumor.

Ganglioglioma is a common CNS tumor in children, mostly found in the temporal lobe, causing epilepsy. Spinal gangliogliomas are very rare, accounting for 1.1% of all intramedullary spinal tumors. The management principles and the need for adjuvant therapy are not yet well defined in this cohort. BRAF V600E mutation in spinal ganglioglioma has been described in a few series recently. In this report, we describe 3 children with spinal ganglioglioma at different locations, and their expression of BRAF V600E mutation and follow-up. In addition, we review the recent literature on pediatric spinal ganglioglioma management.

LIN28A, a sensitive immunohistochemical marker for Embryonal Tumor with Multilayered Rosettes (ETMR), is also positive in a subset of Atypical Teratoid/Rhabdoid Tumor (AT/RT).

INTRODUCTION: CNS embryonal tumors comprise a group of highly malignant neoplasms with a wide spectrum of histomorphological entities that includes Medulloblastoma (MB), Atypical Teratoid/Rhabdoid Tumor (AT/RT), Neuroblastoma (NB), Ganglioneuroblastoma (GNB), Embryonal Tumor with Multilayered Rosettes (ETMR), and the embryonal tumor-Not Otherwise Specified (NOS). The entity ETMR includes previously described histopathologic patterns-Embryonal Tumor with Abundant Neuropil and True Rosettes (ETANTR), Ependymoblastoma (EBL), and Medulloepithelioma (MEPL). Based on the histopathological similarities (multilayered rosettes) among ETANTR, EBL, and MEPL, as well as uniform clinical behavior and common molecular genetic characteristics, the WHO revision has created a new entity, "ETMR." Immunoreactivity of LIN28A has been identified as a sensitive tool for the diagnosis of this entity. Since there is a paucity of literature regarding immunoreactivity of LIN28A across all embryonal CNS tumors, the present study was undertaken. MATERIALS AND METHODS: During the 5-year study period (2012 to 2016), all the embryonal tumors (MB, AT/RT, other embryonal tumors-ETANTR, MEPL, PNET) that had been earlier diagnosed in the department of neuropathology (cases operated in our institute as well as received as referral) were reviewed. The archived Hematoxylin and Eosin (H&E) and the available immunohistochemistry (IHC) sections were studied. Further, for the other embryonal tumors where the paraffin blocks were available, an extended panel of IHC was performed for confirming the diagnosis of embryonal tumor and only confirmed cases were included in the study. The demographic details of the study cohort were noted. IHC for LIN28A was performed on conventional sections. RESULTS: A total of 396 cases of embryonal tumors including 302 MB, 72 AT/RT, and 22 other embryonal tumors were diagnosed during the study period. Among these, 80 MB, 35 AT/RT, 4 ETANTR, 1 MEPL, 4 NB, 2 GNB, and 1 CNS embryonal tumor-NOS (total-127) were included for the study. LIN28A immunoreactivity was absent in all MB, GNB, NB, and CNS embryonal tumors-NOS whereas all cases of ETMR (4 ETANTR, 1 MEPL) and 8/35 (23%) of AT/RT showed immunopositivity for LIN28A, which was patchy and distinct in most of the cases of ETMR. CONCLUSION: Our study reiterates that LIN28A is a sensitive IHC marker for the diagnosis of ETMR. We also show that among CNS embryonal tumors, LIN28A is not specific to ETMRs and such immunoreactivity can also be seen in a proportion of AT/RTs.

Choroid plexus tuberculoma. Diagnosis, management and role of endoscopy.

Ventricular involvement in central nervous system tuberculosis can be in the form of tuberculous ependymitis, intraventricular tuberculoma, intraventricular tuberculous abscess, choroid plexitis and choroid plexus tuberculoma. Only a few cases of choroid plexus tuberculomas have been described and even more rare is the description of the role of endoscopy in management of intraventricular tuberculomas. We report a 33-year-old patient while on treatment for tubercular meningitis who developed a left side choroid plexus lesion with loculated temporal horn. To confirm the diagnosis, endoscopic biopsy of the lesion was carried out. The final histopathology was tuberculoma. Intraventricular tuberculomas are usually associated with recalcitrant lesions, probably due to the poor drug levels within the CSF or as an indirect effect of immune resistance and biopsy becomes important to rule out other possibilities.

Childhood-Onset Myopathy With Preserved Ambulation Caused by a Recurrent ADSSL1 Missense Variant.

Background and Objectives: Distal myopathies are a heterogeneous group of primary muscle disorders with recessive or dominant inheritance. ADSSL1 is a muscle-specific adenylosuccinate synthase isoform involved in adenine nucleotide synthesis. Recessive pathogenic variants in the ADSSL1 gene located in chromosome 14q32.33 cause a distal myopathy phenotype. In this study, we present the clinical and genetic attributes of 6 Indian patients with this myopathy. Methods: This was a retrospective study describing on Indian patients with genetically confirmed ADSSL1 myopathy. Details were obtained from the medical records. Results: All patients presented in their first or early second decade. All had onset in the first decade with a mean age at presentation being 17.7 ± 8.4 years (range: 3-27 years) and M:F ratio being 1:2. The mean disease duration was 9.3 ± 5.2 years ranging from 2 to 15 years. All patients were ambulant with wheelchair bound state in 1 patient due to respiratory involvement. The median serum creatine kinase (CK) level was 185.5 IU/L (range: 123-1564 IU/L). In addition to salient features of ptosis, cardiac involvement, bulbar weakness, and proximo-distal limb weakness with fatigue, there were significant seasonal fluctuations and decremental response to repetitive nerve stimulation, which have not been previously reported. Muscle histopathology was heterogenous with the presence of rimmed vacuoles, nemaline rods, intracellular lipid droplets along with chronic myopathic changes. Subtle response to pyridostigmine treatment was reported. While 5 of 6 patients had homozygous c.781G>A (p.Asp261Asn) variation, 1 had homozygous c.794G>A (p.Gly265Glu) in ADSSL1 gene. Discussion: This study expands the phenotypic spectrum and variability of ADSSL1 myopathy with unusual manifestations in this rare disorder. Because the variant c.781G>A (p.Asp261Asn) is the most common mutation among Indian patients similar to other Asian cohorts, this finding could be useful for genetic screening of suspected patients.

Bing Neel syndrome presenting as isolated cranial nerve palsies - a case report.

Background and aims: Waldenstroms macroglobulinemia (WM) is a low-grade B cell neoplasm. Bing Neel syndrome is a rare manifestation of WM characterized by infiltrative involvement of the central nervous system. Case report: 64-year-old man, presented with 4 years history of slowly progressive diplopia and ptosis of eyes. Examination showed left oculomotor (internal and external ophthalmoplegia), with trochlear, abducens, and right partial oculomotor and abducens nerve involvement. Evaluation showed anemia of hemoglobin 10.7 g/dL, raised erythrocyte sedimentation rate of 120 mm/h and plasma albumin:globulin reversal. Serum protein electrophoresis showed a paraprotein peak in the early gamma region with elevated IgM level (3810 mg/dL) and elevated free kappa light chain level (70.1 mg/L). Bone marrow aspiration from posterior iliac crest revealed mature small lymphocytes with positive immunohistochemical markers of CD5, CD10 negativity and MYD88 mutation positivity suggestive of WM. Patient was treated with bendamustine and rituximab regimen, with no neurological improvement at the end of one year. Conclusion: This case expands spectrum of paraproteinemic neuropathy to include cranial nerve palsy. Thus, plasma cell dyscrasias have to be considered in patients with isolated ophthalmoparesis especially in elderly patients, even with other comorbidities such as diabetes mellitus.

Partial loss of desmin expression due to a leaky splice site variant in the human DES gene is associated with neuromuscular transmission defects.

Recessive desminopathies are rare and often present as severe early-onset myopathy. Here we report a milder phenotype in three unrelated patients from southern India (2 M, 1F) aged 16, 21, and 22 years, who presented with childhood-onset, gradually progressive, fatigable limb-girdle weakness, ptosis, speech and swallowing difficulties, without cardiac involvement. Serum creatine kinase was elevated, and repetitive nerve stimulation showed decrement in all. Clinical improvement was noted with pyridostigmine and salbutamol in two patients. All three patients had a homozygous substitution in intron 5: DES(NM_001927.4):c.1023+5G>A, predicted to cause a donor splice site defect. Muscle biopsy with ultrastructural analysis suggested myopathy with myofibrillar disarray, and immunohistochemistry showed partial loss of desmin with some residual staining, while western blot analysis showed reduced desmin. RT-PCR of patient muscle RNA revealed two transcripts: a reduced normal desmin transcript and a larger abnormal transcript suggesting leaky splicing at the intron 5 donor site. Sequencing of the PCR products confirmed the inclusion of intron 5 in the longer transcript, predicted to cause a premature stop codon. Thus, we provide evidence for a leaky splice site causing partial loss of desmin associated with a unique phenotypic presentation of a milder form of desmin-related recessive myopathy overlapping with congenital myasthenic syndrome.

Phenotype Genotype Characterization of FKRP-related Muscular Dystrophy among Indian Patients.

BACKGROUND: The phenotypic spectrum of Fukutin-related protein (FKRP) mutations is highly variable and comprises of limb girdle muscular dystrophy (LGMD) R9 (previously LGMD 2I) and FKRP related congenital muscular dystrophies. OBJECTIVE: To identify the distinct genotype phenotype pattern in Indian patients with FKRP gene mutations. METHODS: We retrospectively reviewed the case files of patients with muscular dystrophy having a genetically confirmed FKRP mutation. All patients had undergone genetic testing using next-generation sequencing. RESULTS: Our patients included five males and four females presenting between 1.5 years and seven years of age (median age - 3 years). The initial symptom was a delayed acquisition of gross motor developmental milestones in seven patients and recurrent falls and poor sucking in one patient each. Two patients had a language delay, with both having abnormalities on the brain MRI. Macroglossia, scapular winging, and facial weakness were noted in one, three and four patients respectively. Calf muscle hypertrophy was seen in eight patients and ankle contractures in six. At the last follow-up, three patients had lost ambulation (median age - 7 years; range 6.5-9 years) and three patients had not attained independent ambulation. Creatine kinase levels ranged between 2793 and 32,396 U/L (mean 12,120 U/L). A common mutation - c.1343C>T was noted in 5 patients in our cohort. Additionally, four novel mutations were identified. Overall, six patients had an LGMD R9 phenotype, and three had a congenital muscular dystrophy phenotype. CONCLUSION: Patients with FKRP mutations can have varied presentations. A Duchenne-like phenotype was the most commonly encountered pattern in our cohort, with c.1343C>T being the most common mutation.

TEFM variants impair mitochondrial transcription causing childhood-onset neurological disease.

Mutations in the mitochondrial or nuclear genomes are associated with a diverse group of human disorders characterized by impaired mitochondrial respiration. Within this group, an increasing number of mutations have been identified in nuclear genes involved in mitochondrial RNA biology. The TEFM gene encodes the mitochondrial transcription elongation factor responsible for enhancing the processivity of mitochondrial RNA polymerase, POLRMT. We report for the first time that TEFM variants are associated with mitochondrial respiratory chain deficiency and a wide range of clinical presentations including mitochondrial myopathy with a treatable neuromuscular transmission defect. Mechanistically, we show muscle and primary fibroblasts from the affected individuals have reduced levels of promoter distal mitochondrial RNA transcripts. Finally, tefm knockdown in zebrafish embryos resulted in neuromuscular junction abnormalities and abnormal mitochondrial function, strengthening the genotype-phenotype correlation. Our study highlights that TEFM regulates mitochondrial transcription elongation and its defect results in variable, tissue-specific neurological and neuromuscular symptoms.