Increased Probability of Co-Occurrence of Two Rare Diseases in Consanguineous Families and Resolution of a Complex Phenotype by Next Generation Sequencing

Cochleovestibular Phenotype in a Rare Genetic MED13L Mutation

The gene MED13 participates in transcription. The MED13L gene is a paralog of MED13 that is involved in developmental gene expression. Mutations in the gene have been shown to result in a heterogenous phenotype affecting several physiological systems. Hearing loss has been reported very rarely, and vestibular weakness has never been reported in the condition. In this report, we present a mutation of MED13L in c.1162A > T (p.Arg388Ter), where we detail and describe a cochleovestibular phenotype with objective vestibulometry for the first time. The child showed bilateral sloping sensorineural hearing loss, a bilateral vestibular weakness, and an inner ear vestibular structural abnormality on imaging. Early intervention with hearing aids and vestibular rehabilitation led to a favorable outcome in terms of speech, communication, and balance. We emphasize the importance of comprehensive audiovestibular assessment in children diagnosed with MED13L mutations for effective management of these children.

Co-occurrence of Spondyloepiphyseal Dysplasia and X-Linked Hypophosphatemia in a Three-Generation Chinese Family

Rare genetic skeletal disorders (GSDs) remain the major problem in orthopedics and result in significant morbidity in patients, but the causes are highly diverse. Precise molecular diagnosis will benefit management and genetic counseling. This study aims to share the diagnostic experience on a three-generation Chinese family with co-occurrence of spondyloepiphyseal dysplasia (SED) and X-linked hypophosphatemia (XLH), and evaluate the therapeutic effects of two third-generation siblings. The proband, his younger brother, and mother presented with short stature, skeletal problems, and hypophosphatemia. His father, paternal grandfather, and aunt also manifested short stature and skeletal deformities. Whole exome sequencing (WES) of proband-brother-parents initially only found the proband and his younger brother had a pathogenic c.2833G > A(p.G945S) variant in the COL2A1 gene inherited from their father. Re-analysis of WES uncovered the proband and his younger brother also harbored a pathogenic ex.12 del variant in the PHEX gene transmitted from their mother. Sanger sequencing, agarose gel electrophoresis, and quantitative polymerase chain reaction proved these results. The proband and his younger brother were confirmed to have a paternally inherited SED and a maternally inherited XLH. During a 2.8-year follow-up, these two siblings remained short stature and hypophosphatemia, but their radiographic signs and serum bone alkaline phosphatase levels were improved with treatment of oral phosphate and calcitriol. Our study presents the first report of co-occurrence of SED and XLH, shows the possibility that two different rare GSDs co-exist in a single patient, and alerts clinicians and geneticists to be cautious about this condition. Our study also suggests that next-generation sequencing has limit in detecting exon-level large deletions.

The Coexistence of Two Genetic Astrocytopathies-Megalencephalic Leukoencephalopathy and Vanishing White Matter Disease-in an Indian Child

A 9-month-old male child, born of second-degree consanguinity, presented with a progressively enlarging head since early infancy. The child had normal early development, but further acquisition of milestones after 6 months was delayed. He had afebrile seizures at 9 months, followed by the appearance of appendicular spasticity. First magnetic resonance imaging (MRI) showed nonenhancing, diffuse, bilaterally symmetrical T1/fluid-attenuated inversion recovery (FLAIR) hypointensity and T2 hyperintensity of the cerebral white matter and anterior temporal cysts. Subsequently, the periventricular and deep white matter developed microcystic changes with a pattern of radial stripes. Next-generation sequencing revealed homozygous autosomal recessive variations in the MLC1 gene [c.188T > G, (p.Leu63Arg)] on exon 3 and also in the EIF2B3 gene [c.674G > A, (p.Arg225Gln)] on exon 7, the parents being heterozygous carriers for both variations. This article highlights the rare occurrence of two leukodystrophies of diverse pathogenesis in a child from a nonpredisposed community.

Pathogenic Variants Associated with Rare Monogenic Diseases Established in Ancient Neanderthal and Denisovan Genome-Wide Data

Ancient anatomically modern humans (AMHs) encountered other archaic human species, most notably Neanderthals and Denisovans, when they left Africa and spread across Europe and Asia ~60,000 years ago. They interbred with them, and modern human genomes retain DNA inherited from these interbreeding events. High quality (high coverage) ancient human genomes have recently been sequenced allowing for a direct estimation of individual heterozygosity, which has shown that genetic diversity in these archaic human groups was very low, indicating low population sizes. In this study, we analyze ten ancient human genome-wide data, including four sequenced with high-coverage. We screened these ancient genome-wide data for pathogenic mutations associated with monogenic diseases, and established unusual aggregation of pathogenic mutations in individual subjects, including quadruple homozygous cases of pathogenic variants in the PAH gene associated with the condition phenylketonuria in a ~120,000 years old Neanderthal. Such aggregation of pathogenic mutations is extremely rare in contemporary populations, and their existence in ancient humans could be explained by less significant clinical manifestations coupled with small community sizes, leading to higher inbreeding levels. Our results suggest that pathogenic variants associated with rare diseases might be the result of introgression from other archaic human species, and archaic admixture thus could have influenced disease risk in modern humans.

Co-occurrence of neurofibromatosis type 1 and pseudoachondroplasia - a first case report

BACKGROUND

Neurofibromatosis type 1 and pseudoachondroplasia are both rare autosomal dominant disorders, caused by pathogenic mutations in NF1 and COMP genes, respectively. Both neurofibromin 1 and cartilage oligomeric matrix protein (COMP) play a role in the development of the skeleton. Carrying both germline mutations has not been previously reported; however, it can affect the developing phenotype.

CASE PRESENTATION

The index patient, an 8-year-old female presented with several skeletal and dermatologic anomalies resembling the coexistence of multiple syndromes. Her mother had dermatologic symptoms characteristic for neurofibromatosis type 1, and her father presented with distinct skeletal anomalies. NGS-based analysis revealed a heterozygous pathogenic mutation in genes NF1 and COMP in the index patient. A previously unreported heterozygous variant was detected for the NF1 gene. The sequencing of the COMP gene revealed a previously reported, pathogenic heterozygous variant that is responsible for the development of the pseudoachondroplasia phenotype.

CONCLUSIONS

Here, we present the case of a young female carrying pathogenic NF1 and COMP mutations, diagnosed with two distinct heritable disorders, neurofibromatosis type 1 and pseudoachondroplasia. The coincidence of two monogenic autosomal dominant disorders is rare and can pose a differential diagnostic challenge. To the best of our knowledge, this is the first reported co-occurrence of these syndromes.

Bone Quality in Patients with a Congenital Myopathy: A Scoping Review

BACKGROUND

Congenital myopathies are rare neuromuscular disorders presenting with a wide spectrum of clinical features, including long bone fractures (LBFs) that negatively influence functional prognosis, quality of life and survival. Systematic research on bone quality in these patients is lacking.

OBJECTIVE

This scoping review aims to summarize all evidence on bone quality and to deduce recommendations for bone quality management in congenital myopathies.

METHODS

Five electronic databases (Pubmed, Embase, Cochrane, Web of Science, CINAHL) were searched. All studies on bone quality in congenital myopathies were included. Decreased bone quality was defined as low bone mineral density and/or (fragility) LBFs. Study selection and data extraction were performed by three independent reviewers.

RESULTS

We included 244 single cases (mean: 4.1±7.6 years; median: 0 years) diagnosed with a congenital myopathy from 35 articles. Bone quality was decreased in 93 patients (37%) (mean: 2.6±6.8 years; median: 0 years). Low bone mineral density was reported in 11 patients (4.5%) (mean: 10.9±9.7; median: 11 years). Congenital LBFs were reported in 64 patients (26%). (Fragility) LBFs later at life were described in 24 patients (9.8%) (mean: 14.9±11.0; median: 14 years). Four cases (1.6%) were reported to receive vitamin D and/or calcium supplementation or diphosphonate administration.

CONCLUSION

LBFs are thus frequently reported in congenital myopathies. We therefore recommend optimal bone quality management through bone mineral density assessment, vitamin D and calcium suppletion, and referral to internal medicine or pediatrics for consideration of additional therapies in order to prevent complications of low bone mineral density.

[A case of spastic paraplegia with SPG4 and SPG3 associated mutations]

A rare case of autosomal dominant spastic paraplegia in a 36-year-old female with two reported earlier mutations of most common spastic paraplegia forms: SPG4 (mutation p.Cys28Leufs*20 in SPAST gene) and SPG3 (mutation p.Val405Met in ATL1 gene) is presented. The mutations detected by massively parallel sequencing (MPS) panel were inherited from affected mother and clinically unaffected father, respectively. The proband, her 61-year-old mother and deceased grandfather had 'uncomplicated' paraplegia with onset in 4^th decade. The 67-year-old father had no even minimal subclinical signs of the disease and no affected relatives, detection of his low-penetrating ATL1 mutation was unexpected. MPS methods are the most informative for identifying a patient and/or family members with a combined hereditary neurological pathology, especially a combination of similar forms of heterogeneous groups, such as spastic paraplegia.

Hereditary thrombotic thrombocytopenic purpura (TTP) with co-occurring autosomal dominant polycystic kidney disease (ADPKD)

Hereditary thrombotic thrombocytopenic purpura (TTP) and autosomal dominant polycystic kidney disease (ADPKD) are two distinct genetic diseases that may affect the kidneys through different mechanisms. ADPKD is a common genetic disorder that leads to exponential formation and growth of cysts replacing all segments of nephrons. Hereditary TTP is a rare autosomal recessive disorder that leads to the disseminated formation of arteriolar platelet-rich thrombi, which produce manifestations of various organs dysfunction. We present a case of a pregnant female with hereditary TTP co-occurring with ADPKD. To our knowledge, this is the first case in the literature describing the co-occurrence of ADPKD and hereditary TTP. We aim to describe the clinical course including the renal and the pregnancy outcomes, describe the consanguinity and family history, and try to explain the potential effect of one disease on the clinical course of the other.

Recessive PRDM13 mutations cause fatal perinatal brainstem dysfunction with cerebellar hypoplasia and disrupt Purkinje cell differentiation

Pontocerebellar hypoplasias (PCHs) are congenital disorders characterized by hypoplasia or early atrophy of the cerebellum and brainstem, leading to a very limited motor and cognitive development. Although over 20 genes have been shown to be mutated in PCHs, a large proportion of affected individuals remains undiagnosed. We describe four families with children presenting with severe neonatal brainstem dysfunction and pronounced deficits in cognitive and motor development associated with four different bi-allelic mutations in PRDM13, including homozygous truncating variants in the most severely affected individuals. Brain MRI and fetopathological examination revealed a PCH-like phenotype, associated with major hypoplasia of inferior olive nuclei and dysplasia of the dentate nucleus. Notably, histopathological examinations highlighted a sparse and disorganized Purkinje cell layer in the cerebellum. PRDM13 encodes a transcriptional repressor known to be critical for neuronal subtypes specification in the mouse retina and spinal cord but had not been implicated, so far, in hindbrain development. snRNA-seq data mining and in situ hybridization in humans show that PRDM13 is expressed at early stages in the progenitors of the cerebellar ventricular zone, which gives rise to cerebellar GABAergic neurons, including Purkinje cells. We also show that loss of function of prdm13 in zebrafish leads to a reduction in Purkinje cells numbers and a complete absence of the inferior olive nuclei. Altogether our data identified bi-allelic mutations in PRDM13 as causing a olivopontocerebellar hypoplasia syndrome and suggest that early deregulations of the transcriptional control of neuronal fate specification could contribute to a significant number of cases.

Identification of a Novel Missense Mutation of the PHEX Gene in a Large Chinese Family with X-Linked Hypophosphataemia

X-linked hypophosphataemia (XLH) is an X-linked dominant rare disease that refers to the most common hereditary hypophosphatemia (HH) caused by mutations in the phosphate-regulating endopeptidase homolog X-linked gene (PHEX; OMIM: * 300550). However, mutations that have already been reported cannot account for all cases of XLH. Extensive genetic analysis can thus be helpful for arriving at the diagnosis of XLH. Herein, we identified a novel heterozygous mutation of PHEX (NM_000444.5: c.1768G > A) in a large Chinese family with XLH by whole-exome sequencing (WES). In addition, the negative effect of this mutation in PHEX was confirmed by both bioinformatics analysis and in vitro experimentation. The three-dimensional protein-model analysis predicted that this mutation might impair normal zinc binding. Immunofluorescence staining, qPCR, and western blotting analysis confirmed that the mutation we detected attenuated PHEX protein expression. The heterozygous mutation of PHEX (NM_000444.5: c.1768G > A) identified in this study by genetic and functional experiments constitutes a novel genetic cause of XLH, but further study will be required to expand its use in clinical and molecular diagnoses of XLH.

Methods to Improve Molecular Diagnosis in Genomic Cold Cases in Pediatric Neurology

During the last decade, genetic testing has emerged as an important etiological diagnostic tool for Mendelian diseases, including pediatric neurological conditions. A genetic diagnosis has a considerable impact on disease management and treatment; however, many cases remain undiagnosed after applying standard diagnostic sequencing techniques. This review discusses various methods to improve the molecular diagnostic rates in these genomic cold cases. We discuss extended analysis methods to consider, non-Mendelian inheritance models, mosaicism, dual/multiple diagnoses, periodic re-analysis, artificial intelligence tools, and deep phenotyping, in addition to integrating various omics methods to improve variant prioritization. Last, novel genomic technologies, including long-read sequencing, artificial long-read sequencing, and optical genome mapping are discussed. In conclusion, a more comprehensive molecular analysis and a timely re-analysis of unsolved cases are imperative to improve diagnostic rates. In addition, our current understanding of the human genome is still limited due to restrictions in technologies. Novel technologies are now available that improve upon some of these limitations and can capture all human genomic variation more accurately. Last, we recommend a more routine implementation of high molecular weight DNA extraction methods that is coherent with the ability to use and/or optimally benefit from these novel genomic methods.

Congenital Hypotonia: Cracking a SAGA of consanguineous kindred harboring four genetic variants

BACKGROUND

We aimed to determine the molecular and biochemical basis of an extended highly consanguineous family with multiple children presenting severe congenital hypotonia.

METHODS

Clinical investigations, homozygosity mapping, linkage analyses and whole exome sequencing, were performed. mRNA and protein levels were determined. Population screening was followed.

RESULTS

We have identified a novel nonsense variant in NGLY1 in two affected siblings, and compound heterozygosity for three novel RYR1 variants in two affected sisters from another nuclear family within the broad pedigree. Population screening revealed a high prevalence of carriers for both diseases. The genetic variants were proven to be pathogenic, as demonstrated by western blot analyses.

CONCLUSIONS

Revealing the genetic diagnosis enabled us to provide credible genetic counselling and pre-natal diagnosis to the extended family and genetic screening for this high-risk population. Whole exome/genome sequencing should be the first tier tool for accurate determination of the genetic basis of congenital hypotonia. Two different genetic disorders within a large consanguineous pedigree should be always considered.

Network for Therapy in Rare Epilepsies (NETRE): Lessons From the Past 15 Years

Background: In 2005, Network for Therapy in Rare Epilepsies (NETRE)-was initiated in order to share treatment experiences among clinicians in patients with rare epilepsies. Here we describe the structure of the rapidly growing NETRE and summarize some of the findings of the last 15 years. Methodology/Structure of NETRE: NETRE is organized in distinct groups (currently >270). Starting point is always a patient with a rare epilepsy/ epileptic disorder. This creates a new group, and next, a medical coordinator is appointed. The exchange of experiences is established using a data entry form, which the coordinator sends to colleagues. The primary aim is to exchange experiences (retrospectively, anonymously, MRI results also non-anonymously) of the epilepsy treatment as well as on clinical presentation and comorbidities NETRE is neither financed nor sponsored. Results: Some of the relevant results: (1) first description of FIRES as a new epilepsy syndrome and its further investigation, (2) in SCN2A, the assignment to gain- vs. loss-of-function mutations has a major impact on clinical decisions to use or avoid treatment with sodium channel blockers, (3) the important aspect of avoiding overtreatment in CDKL5 patients, due to loss of effects of anticonvulsants after 12 months, (4) pathognomonic MRI findings in FOXG1 patients, (5) the first description of pathognomonic chewing-induced seizures in SYNGAP1 patients, and the therapeutic effect of statins as anticonvulsant in these patients, (6) the phenomenon of another reflex epilepsy-bathing epilepsy associated with a SYN1 mutation. Of special interest is also a NETRE group following twins with genetic and/or structural epilepsies [including vanishing-twin-syndrome and twin-twin-transfusion syndrome) [= "Early Neuroimpaired Twin Entity" (ENITE)]. Discussion and Perspective: NETRE enables clinicians to quickly exchange information on therapeutic experiences in rare diseases with colleagues at an international level. For both parents and clinicians/scientist this international exchange is both reassuring and helpful. In collaboration with other groups, personalized therapeutic approaches are sought, but the present limitations of currently available therapies are also highlighted. Presently, the PATRE Project (PATient based phenotyping and evaluation of therapy for Rare Epilepsies) is commencing, in which information on therapies will be obtained directly from patients and their caregivers.

Further defining the clinical and molecular spectrum of acromesomelic dysplasia type maroteaux: a Turkish tertiary center experience

Acromesomelic dysplasia type Maroteaux (AMDM, OMIM #602875) is an autosomal recessive disorder characterized by severe short stature, shortened middle and distal segments of the limbs, redundant skin of fingers, radial head subluxation or dislocation, large great toes and cranium, and normal intelligence. Only the skeletal system appears to be consistently affected. AMDM is caused by biallelic loss-of-function variants in the natriuretic peptide receptor B (NPRB or NPR2, OMIM #108961) which is involved in endochondral ossification and longitudinal growth of limbs and vertebrae. In this study, we investigated 26 AMDM patients from 22 unrelated families and revealed their genetic etiology in 20 families, via Sanger sequencing or exome sequencing. A total of 22 distinct variants in NPR2 (14 missense, 5 nonsense, 2 intronic, and 1 one-amino acid deletion) were detected, among which 15 were novel. They were in homozygous states in 19 patients and in compound heterozygous states in four patients. Parents with heterozygous NPR2 variants were significantly shorter than the control. Extra-skeletal abnormalities, including global developmental delay/intellectual disability, nephrolithiasis, renal cyst, and oligodontia were noted in the patient cohort. The high parental consanguinity rate might have contributed to these findings, probably associated with other gene variants. This study represents the largest cohort of AMDM from Turkey and regional countries and further expands the molecular and clinical spectrum of AMDM.

CLN5 in heterozygosis may protect against the development of tumors in a VHL patient

Von Hippel-Lindau syndrome (VHL) is a rare disease of dominant inheritance that increases susceptibility to tumor development, with a complete penetrance at the age of 60. In this report, we present the unprecedented case of a VHL carrier who remains healthy at 72. Under the course of this study, it was discovered that this patient carries a mutation for a second rare disease, Neuronal Ceroid Lipofuscinosis (NCL or CNL). We hypothesize that the CLN mutation she carries offers a protective effect, preventing tumor development in the cells potentially suffering a VHL second hit mutation. To test this hypothesis, we ran a series of molecular experiments and confirmed that cell viability of primary endothelial cells decreases upon CLN5 silencing. Our results further elucidate the cell biology implications of two rare diseases interacting.

Clinical practice recommendations for the diagnosis and management of X-linked hypophosphataemia

X-linked hypophosphataemia (XLH) is the most common cause of inherited phosphate wasting and is associated with severe complications such as rickets, lower limb deformities, pain, poor mineralization of the teeth and disproportionate short stature in children as well as hyperparathyroidism, osteomalacia, enthesopathies, osteoarthritis and pseudofractures in adults. The characteristics and severity of XLH vary between patients. Because of its rarity, the diagnosis and specific treatment of XLH are frequently delayed, which has a detrimental effect on patient outcomes. In this Evidence-Based Guideline, we recommend that the diagnosis of XLH is based on signs of rickets and/or osteomalacia in association with hypophosphataemia and renal phosphate wasting in the absence of vitamin D or calcium deficiency. Whenever possible, the diagnosis should be confirmed by molecular genetic analysis or measurement of levels of fibroblast growth factor 23 (FGF23) before treatment. Owing to the multisystemic nature of the disease, patients should be seen regularly by multidisciplinary teams organized by a metabolic bone disease expert. In this article, we summarize the current evidence and provide recommendations on features of the disease, including new treatment modalities, to improve knowledge and provide guidance for diagnosis and multidisciplinary care.

In this Evidence-Based Guideline on X-linked hypophosphataemia, the authors identify the criteria for diagnosis of this disease, provide guidance for medical and surgical treatment and explain the challenges of follow-up.

ADA2 deficiency in a patient with Noonan syndrome-like disorder with loose anagen hair: The co-occurrence of two rare syndromes

Noonan syndrome-like disorder with loose anagen hair (NS/LAH) is one of the RASopathies, a group of clinically related developmental disorders caused by germline mutations in genes that encode components acting in the RAS/MAPK pathway. Among RASopathies, NS/LAH (OMIM 607721) is an extremely rare, multiple anomaly syndrome characterized by dysmorphic facial features similar to those observed in Noonan syndrome along with some distinctive ectodermal findings including easily pluckable, sparse, thin, and slow-growing hair. ADA2 deficiency (DADA2, OMIM 615688) is a monogenic autoinflammatory disorder caused by homozygous or compound heterozygous mutations in ADA2, with clinical features including recurrent fever, livedo racemosa, hepatosplenomegaly, and strokes as well as immune dysregulation. This is the first report of NS/LAH and ADA2 deficiency in the same individual. We report on a patient presenting with facial features, recurrent infections and ectodermal findings in whom both the clinical and molecular diagnoses of NS/LAH and ADA2 deficiency were established, respectively.

GLI1 inactivation is associated with developmental phenotypes overlapping with Ellis-van Creveld syndrome

GLI1, GLI2 and GLI3 form a family of transcription factors which regulate development by mediating the action of Hedgehog (Hh) morphogens. Accordingly, inactivating variants in GLI2 and GLI3 are found in several developmental disorders. In contrast, loss-of-function mutations in GLI1 have remained elusive, maintaining enigmatic the role of this gene in the human embryo. We describe eight patients from three independent families having biallelic truncating variants in GLI1 and developmental defects overlapping with Ellis-van Creveld syndrome (EvC), a disease caused by diminished Hh signaling. Two families had mutations in the last exon of the gene and a third family was identified with an N-terminal stop gain variant predicted to be degraded by the NMD-pathway. Analysis of fibroblasts from one of the patients with homozygous C-terminal truncation of GLI1 demonstrated that the corresponding mutant GLI1 protein is fabricated by patient cells and becomes upregulated in response to Hh signaling. However, the transcriptional activity of the truncated GLI1 factor was found to be severely impaired by cell culture and in vivo assays, indicating that the balance between GLI repressors and activators is altered in affected subjects. Consistent with this, reduced expression of the GLI target PTCH1 was observed in patient fibroblasts after chemical induction of the Hh pathway. We conclude that GLI1 inactivation is associated with a phenotypic spectrum extending from isolated postaxial polydactyly to an EvC-like condition.

NGS Technologies as a Turning Point in Rare Disease Research , Diagnosis and Treatment

Approximately 25-50 million Americans, 30 million Europeans, and 8% of the Australian population have a rare disease. Rare diseases are thus a common problem for clinicians and account for enormous healthcare costs worldwide due to the difficulty of establishing a specific diagnosis. In this article, we review the milestones achieved in our understanding of rare diseases since the emergence of next-generation sequencing (NGS) technologies and analyze how these advances have influenced research and diagnosis. The first half of this review describes how NGS has changed diagnostic workflows and provided an unprecedented, simple way of discovering novel disease-associated genes. We focus particularly on metabolic and neurodevelopmental disorders. NGS has enabled cheap and rapid genetic diagnosis, highlighted the relevance of mosaic and de novo mutations, brought to light the wide phenotypic spectrum of most genes, detected digenic inheritance or the presence of more than one rare disease in the same patient, and paved the way for promising new therapies. In the second part of the review, we look at the limitations and challenges of NGS, including determination of variant causality, the loss of variants in coding and non-coding regions, and the detection of somatic mosaicism variants and epigenetic mutations, and discuss how these can be overcome in the near future.

Recessive mutation in EXOSC3 associates with mitochondrial dysfunction and pontocerebellar hypoplasia

Recessive mutations in EXOSC3, encoding a subunit of the human RNA exosome complex, cause pontocerebellar hypoplasia type 1b (PCH1B). We report a boy with severe muscular hypotonia, psychomotor retardation, progressive microcephaly, and cerebellar atrophy. Biochemical abnormalities comprised mitochondrial complex I and pyruvate dehydrogenase complex (PDHc) deficiency. Whole exome sequencing uncovered a known EXOSC3 mutation p.(D132A) as the underlying cause. In patient fibroblasts, a large portion of the EXOSC3 protein was trapped in the cytosol. MtDNA copy numbers in muscle were reduced to 35%, but mutations in the mtDNA and in nuclear mitochondrial genes were ruled out. RNA-Seq of patient muscle showed highly increased mRNA copy numbers, especially for genes encoding structural subunits of OXPHOS complexes I, III, and IV, possibly due to reduced degradation by a dysfunctional exosome complex. This is the first case of mitochondrial dysfunction associated with an EXOSC3 mutation, which expands the phenotypic spectrum of PCH1B. We discuss the links between exosome and mitochondrial dysfunction.

Fatal familial insomnia with abnormal signals on routine MRI: a case report and literature review

Background

Fatal familial insomnia (FFI) is a rare autosomal dominant disease caused by the PRNP D178N/129 M mutation. Routine brain CT and MRI usually reveal non-specific features. We report a patient with FFI presenting with diffuse abnormal signals on MRI, later confirmed as combined with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL).

Case presentation

The patient was a 58-year-old female, whose main clinical manifestations were insomnia, movement disorders, autonomic hyperactivity and mental deterioration. The patient also suffered a typical episode of transient global amnesia. MRI indicated a diffuse white matter abnormality and microbleeding on the susceptibility-weighted imaging. On biopsy, the brain tissue sections showed spongiform changes with gliosis, neuronal degeneration, and prion protein deposition in a portion of the neurons. In addition, arteriosclerosis was prominent. Transmission electron microscopy showed osmiophilic particle deposition in the matrix of medial smooth muscle cells. Gene sequencing confirmed a diagnosis of FFI with CADASIL.

Conclusions

This case is a compelling example that even with evidence of leukoencephalopathy, prion disease should be an important differential diagnosis of rapidly progressive dementia and related diseases. In cases of genetic diseases with atypical manifestations, the coexistence of two or even more diseases should be considered as a possible explanation.

New CDH3 mutation in the first Spanish case of hypotrichosis with juvenile macular dystrophy, a case report

Background

CDH3 on 16q22.1 is responsible for two rare autosomal recessive disorders with hypotrichosis and progressive macular dystrophy: Hypotrichosis with Juvenile Macular Dystrophy and Ectodermal Dysplasia, Ectrodactyly and Macular Dystrophy. We present a new case of Hypotrichosis with Juvenile Macular Dystrophy.

Case presentation

A Spanish male born in 1998 from non-consanguineous healthy parents with a suspected diagnosis of Keratosis Follicularis Spinulosa Decalvans and Retinitis Pigmentosa Inversa referred to our Genetics Department (IIS-Fundación Jiménez Díaz).

Molecular study of ABCA4 was performed, and a heterozygous missense p.Val2050Leu variant in ABCA4 was found.

Clinical revision reclassified this patient as Hypotrichosis with Juvenile Macular Dystrophy. Therefore, further CDH3 sequencing was performed showing a novel maternal missense change p.Val205Met (probably pathogenic by in silico analysis), and a previously reported paternal frameshift c.830del;p.Gly277Alafs*20, thus supporting the clinical diagnosis..

Conclusions

This is not only the first Spanish case with this clinical and molecular diagnosis, but a new mutation has been described in CDH3. Moreover, this work reflects the importance of joint assessment of clinical signs and evaluation of pedigree for a correct genetic study approach and diagnostic.

A novel TRAPPC11 mutation in two Turkish families associated with cerebral atrophy, global retardation, scoliosis, achalasia and alacrima

BACKGROUND

Triple A syndrome (MIM #231550) is associated with mutations in the AAAS gene. However, about 30% of patients with triple A syndrome symptoms but an unresolved diagnosis do not harbour mutations in AAAS.

OBJECTIVE

Search for novel genetic defects in families with a triple A-like phenotype in whom AAAS mutations are not detected.

METHODS

Genome-wide linkage analysis, whole-exome sequencing and functional analyses were used to discover and verify a novel genetic defect in two families with achalasia, alacrima, myopathy and further symptoms. Effect and pathogenicity of the mutation were verified by cell biological studies.

RESULTS

We identified a homozygous splice mutation in TRAPPC11 (c.1893+3A>G, [NM_021942.5], g.4:184,607,904A>G [hg19]) in four patients from two unrelated families leading to incomplete exon skipping and reduction in full-length mRNA levels. TRAPPC11 encodes for trafficking protein particle complex subunit 11 (TRAPPC11), a protein of the transport protein particle (TRAPP) complex. Western blot analysis revealed a dramatic decrease in full-length TRAPPC11 protein levels and hypoglycosylation of LAMP1. Trafficking experiments in patient fibroblasts revealed a delayed arrival of marker proteins in the Golgi and a delay in their release from the Golgi to the plasma membrane. Mutations in TRAPPC11 have previously been described to cause limb-girdle muscular dystrophy type 2S (MIM #615356). Indeed, muscle histology of our patients also revealed mild dystrophic changes. Immunohistochemically, β-sarcoglycan was absent from focal patches.

CONCLUSIONS

The identified novel TRAPPC11 mutation represents an expansion of the myopathy phenotype described before and is characterised particularly by achalasia, alacrima, neurological and muscular phenotypes.