De novo missense variants in RRAGC lead to a fatal mTORopathy of early childhood.

PURPOSE: Mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) regulates cell growth in response to nutritional status. Central to the mTORC1 function is the Rag-GTPase heterodimer. One component of the Rag heterodimer is RagC (Ras-related GTP-binding protein C), which is encoded by the RRAGC gene. METHODS: Genetic testing via trio exome sequencing was applied to identify the underlying disease cause in 3 infants with dilated cardiomyopathy, hepatopathy, and brain abnormalities, including pachygyria, polymicrogyria, and septo-optic dysplasia. Studies in patient-derived skin fibroblasts and in a HEK293 cell model were performed to investigate the cellular consequences. RESULTS: We identified 3 de novo missense variants in RRAGC (NM_022157.4: c.269C>A, p.(Thr90Asn), c.353C>T, p.(Pro118Leu), and c.343T>C, p.(Trp115Arg)), which were previously reported as occurring somatically in follicular lymphoma. Studies of patient-derived fibroblasts carrying the p.(Thr90Asn) variant revealed increased cell size, as well as dysregulation of mTOR-related p70S6K (ribosomal protein S6 kinase 1) and transcription factor EB signaling. Moreover, subcellular localization of mTOR was decoupled from metabolic state. We confirmed the key findings for all RRAGC variants described in this study in a HEK293 cell model. CONCLUSION: The above results are in line with a constitutive overactivation of the mTORC1 pathway. Our study establishes de novo missense variants in RRAGC as cause of an early-onset mTORopathy with unfavorable prognosis.

Senescent fibro-adipogenic progenitors are potential drivers of pathology in inclusion body myositis.

Inclusion body myositis (IBM) is unique across the spectrum of idiopathic inflammatory myopathies (IIM) due to its distinct clinical presentation and refractoriness to current treatment approaches. One explanation for this resistance may be the engagement of cell-autonomous mechanisms that sustain or promote disease progression of IBM independent of inflammatory activity. In this study, we focused on senescence of tissue-resident cells as potential driver of disease. For this purpose, we compared IBM patients to non-diseased controls and immune-mediated necrotizing myopathy patients. Histopathological analysis suggested that cellular senescence is a prominent feature of IBM, primarily affecting non-myogenic cells. In-depth analysis by single nuclei RNA sequencing allowed for the deconvolution and study of muscle-resident cell populations. Among these, we identified a specific cluster of fibro-adipogenic progenitors (FAPs) that demonstrated key hallmarks of senescence, including a pro-inflammatory secretome, expression of p21, increased ß-galactosidase activity, and engagement of senescence pathways. FAP function is required for muscle cell health with changes to their phenotype potentially proving detrimental. In this respect, the transcriptomic landscape of IBM was also characterized by changes to the myogenic compartment demonstrating a pronounced loss of type 2A myofibers and a rarefication of acetylcholine receptor expressing myofibers. IBM muscle cells also engaged a specific pro-inflammatory phenotype defined by intracellular complement activity and the expression of immunogenic surface molecules. Skeletal muscle cell dysfunction may be linked to FAP senescence by a change in the collagen composition of the latter. Senescent FAPs lose collagen type XV expression, which is required to support myofibers' structural integrity and neuromuscular junction formation in vitro. Taken together, this study demonstrates an altered phenotypical landscape of muscle-resident cells and that FAPs, and not myofibers, are the primary senescent cell type in IBM.

[Neurological complications of hepatitis C infections]. / Neurologische Komplikationen der Hepatitis-C-Infektion.

Chronic hepatitis C virus (HCV) infection is a highly prevalent systemic disease, which can cause a variety of neurological complications. The HCV-associated symptoms can be differentiated into central and peripheral nervous systems as well as the musculature. Important pathomechanisms are HCV-associated autoimmunity (e.g. mixed cryoglobulinemia with polyneuropathy) and direct neurotoxic effects of the virus (e.g. HCV-associated cognitive deficits). Distal symmetric polyneuropathies, small fiber neuropathies and cognitive deficits are the most prevalent neurological manifestations. Furthermore, HCV infection is a risk factor for ischemic and hemorrhagic stroke as well as Parkinson's disease. As HCV infection has become a permanently curable disease in >90% of patients, early identification and antiviral treatment of HCV positive patients is of utmost importance.

Inositol 1,4,5-trisphosphate receptor type 1 autoantibodies in paraneoplastic and non-paraneoplastic peripheral neuropathy.

BACKGROUND: Recently, we described a novel autoantibody, anti-Sj/ITPR1-IgG, that targets the inositol 1,4,5-trisphosphate receptor type 1 (ITPR1) in patients with cerebellar ataxia. However, ITPR1 is expressed not only by Purkinje cells but also in the anterior horn of the spinal cord, in the substantia gelatinosa and in the motor, sensory (including the dorsal root ganglia) and autonomic peripheral nervous system, suggesting that the clinical spectrum associated with autoimmunity to ITPR1 may be broader than initially thought. Here we report on serum autoantibodies to ITPR1 (up to 1:15,000) in three patients with (radiculo)polyneuropathy, which in two cases was associated with cancer (ITPR1-expressing adenocarcinoma of the lung, multiple myeloma), suggesting a paraneoplastic aetiology. METHODS: Serological and other immunological studies, and retrospective analysis of patient records. RESULTS: The clinical findings comprised motor, sensory (including severe pain) and autonomic symptoms. While one patient presented with subacute symptoms mimicking Guillain-Barré syndrome (GBS), the symptoms progressed slowly in two other patients. Electrophysiology revealed delayed F waves; a decrease in motor and sensory action potentials and conduction velocities; delayed motor latencies; signs of denervation, indicating sensorimotor radiculopolyneuropathy of the mixed type; and no conduction blocks. ITPR1-IgG belonged to the complement-activating IgG1 subclass in the severely affected patient but exclusively to the IgG2 subclass in the two more mildly affected patients. Cerebrospinal fluid ITPR1-IgG was found to be of predominantly extrathecal origin. A 3H-thymidine-based proliferation assay confirmed the presence of ITPR1-reactive lymphocytes among peripheral blood mononuclear cells (PBMCs). Immunophenotypic profiling of PBMCs protein demonstrated predominant proliferation of B cells, CD4 T cells and CD8 memory T cells following stimulation with purified ITPR1 protein. Patient ITPR1-IgG bound both to peripheral nervous tissue and to lung tumour tissue. A nerve biopsy showed lymphocyte infiltration (including cytotoxic CD8 cells), oedema, marked axonal loss and myelin-positive macrophages, indicating florid inflammation. ITPR1-IgG serum titres declined following tumour removal, paralleled by clinical stabilization. CONCLUSIONS: Our findings expand the spectrum of clinical syndromes associated with ITPR1-IgG and suggest that autoimmunity to ITPR1 may underlie peripheral nervous system diseases (including GBS) in some patients and may be of paraneoplastic origin in a subset of cases.

Ornithine transcarbamylase deficiency of a male newborn with fatal outcome.

Ornithine transcarbamylase deficiency (OTCD) is the most common malfunction of ureagenesis. The case of a male newborn who died at the age of 2 days for clinically unclear reasons is presented. The post-mortem routine and esoteric testing methods that finally led to the diagnosis of a fatal case of OTCD are outlined here.

Myelin protein zero mutation-related hereditary neuropathies: Neuropathological insight from a new nerve biopsy cohort.

Myelin protein zero (MPZ/P0) is a major structural protein of peripheral nerve myelin. Disease-associated variants in the MPZ gene cause a wide phenotypic spectrum of inherited peripheral neuropathies. Previous nerve biopsy studies showed evidence for subtype-specific morphological features. Here, we aimed at enhancing the understanding of these subtype-specific features and pathophysiological aspects of MPZ neuropathies. We examined archival material from two Central European centers and systematically determined genetic, clinical, and neuropathological features of 21 patients with MPZ mutations compared to 16 controls. Cases were grouped based on nerve conduction data into congenital hypomyelinating neuropathy (CHN; n = 2), demyelinating Charcot-Marie-Tooth (CMT type 1; n = 11), intermediate (CMTi; n = 3), and axonal CMT (type 2; n = 5). Six cases had combined muscle and nerve biopsies and one underwent autopsy. We detected four MPZ gene variants not previously described in patients with neuropathy. Light and electron microscopy of nerve biopsies confirmed fewer myelinated fibers, more onion bulbs and reduced regeneration in demyelinating CMT1 compared to CMT2/CMTi. In addition, we observed significantly more denervated Schwann cells, more collagen pockets, fewer unmyelinated axons per Schwann cell unit and a higher density of Schwann cell nuclei in CMT1 compared to CMT2/CMTi. CHN was characterized by basal lamina onion bulb formation, a further increase in Schwann cell density and hypomyelination. Most late onset axonal neuropathy patients showed microangiopathy. In the autopsy case, we observed prominent neuromatous hyperinnervation of the spinal meninges. In four of the six muscle biopsies, we found marked structural mitochondrial abnormalities. These results show that MPZ alterations not only affect myelinated nerve fibers, leading to either primarily demyelinating or axonal changes, but also affect non-myelinated nerve fibers. The autopsy case offers insight into spinal nerve root pathology in MPZ neuropathy. Finally, our data suggest a peculiar association of MPZ mutations with mitochondrial alterations in muscle.

Morphological and molecular comparison of HIV-associated and sporadic inclusion body myositis.

OBJECTIVE: The molecular characteristics of sporadic inclusion body myositis (sIBM) have been intensively studied, and specific patterns on the cellular, protein and RNA level have emerged. However, these characteristics have not been studied in the context of HIV-associated IBM (HIV-IBM). In this study, we compared clinical, histopathological, and transcriptomic patterns of sIBM and HIV-IBM. METHODS: In this cross-sectional study, we compared patients with HIV-IBM and sIBM based on clinical and morphological features as well as gene expression levels of specific T-cell markers in skeletal muscle biopsy samples. Non-disease individuals served as controls (NDC). Cell counts for immunohistochemistry and gene expression profiles for quantitative PCR were used as primary outcomes. RESULTS: 14 muscle biopsy samples (7 HIV-IBM, 7 sIBM) of patients and 6 biopsy samples from NDC were included. Clinically, HIV-IBM patients showed a significantly lower age of onset and a shorter period between symptom onset and muscle biopsy. Histomorphologically, HIV-IBM patients showed no KLRG1+ or CD57+ cells, while the number of PD1+ cells did not differ significantly between the two groups. All markers were shown to be significantly upregulated at gene expression level with no significant difference between the IBM subgroups. CONCLUSION: Despite HIV-IBM and sIBM sharing important clinical, histopathological, and transcriptomic signatures, the presence of KLRG1+ cells discriminated sIBM from HIV-IBM. This may be explained by longer disease duration and subsequent T-cell stimulation in sIBM. Thus, the presence of TEMRA cells is characteristic for sIBM, but not a prerequisite for the development of IBM in HIV+ patients.

Severe generalised rhabdomyolysis with fatal outcome associated with isotretinoin.

Isotretinoin is considered to be a safe and effective therapy in otherwise therapy-resistant acne. Elevated serum creatine phosphokinase values with or without muscle-related symptoms in isotretinoin-treated patients have been reported and interpreted as benign phenomena, lethal cases have not been described yet. We present the case of a 20-year-old male who died from severe generalised rhabdomyolysis associated with isotretinoin treatment.

Vasculitic multiplex mononeuritis: polyarteritis nodosa versus cryoglobulinemic vasculitis.

A 76-year-old female patient presented with a progressive motor-sensory multiplex mononeuritis (MM). Combined muscle and nerve biopsy showed the typical findings of a polyarteritis nodosa (PAN). Despite treatment with corticosteroids paresthesias increased and purpura of the legs newly appeared. Hepatitis screening revealed chronic hepatitis C-infection associated with cryoglobulinemia Type II (IgM-kappa Ig A). Finally, we diagnosed a hepatitis C-associated cryoglobulinemic vasculitis based on clinical and laboratory findings.

Characteristic clinical and ultrastructural findings in nesprinopathies.

AIMS: To define the neurological and neuropathological alterations caused by SYNE1 mutations. METHODS: We describe 5 patients (3 males, 2 females; age 3-24 years) from 3 families. The diagnostic work-up included three muscle biopsies and two nerve biopsies in three of the cases. RESULTS: Three different phenotypes were discerned. Two patients showed progressive ataxia, mental retardation, neuropathy and radially deviated thumbs (spinocerebellar ataxia, SCAR, type 8 phenotype). Two patients had mild congenital myopathy with restrictive lung disease, clubfeet and thumb anomalies (myopathic arthrogryposis). One patient had congenital myopathy with dilated cardiomyopathy and adducted thumbs (Emery-Dreifuss Muscular Dystrophy, EDMD, type 4). Light microscopy of the three muscle biopsies revealed chronic non-necrotizing myopathy without rimmed vacuoles in all cases combined with neurogenic atrophy in one case. The two nerve biopsies showed predominantly axonal neuropathy with demyelinating features. Nuclear alterations, most notably lobulation and focal widening of the space between inner and outer leaflet of the nuclear envelope, were a prominent consistent feature of myonuclei and Schwann cell nuclei in each of the three muscle specimens and one nerve specimen that could be examined by electron microscopy. CONCLUSION: Thumb abnormalities and nuclear envelope alterations are characteristic for SYNE 1 mutations. Schwann cell nuclei are affected, indicating that such nuclear envelope changes in glial cells contribute to the neurodegenerative phenotype in human nesprinopathies.

Disruption of excitatory amino acid transporters in brains of SIV-infected rhesus macaques is associated with microglia activation.

Glutamate-mediated neurodysfunction in human immunodeficiency virus (HIV) infection has been primarily suggested by in vitro studies. The regulation of glutamatergic neurotransmission in inflammation is a complex interaction between activation of immune mediators and adaptive changes in the functional elements of the glutamatergic synapse. We have used simian immunodeficiency virus (SIV)-infected macaques to answer the questions (i) whether perturbation of glutamate neurotransmission is evident during progression of immunodeficiency disease and (ii) what are the mechanisms underlying this impairment. Disease progression in SIV-infected macaques both in the periphery and in the brain was documented by clinical and general pathological examination, plasma and brain viral RNA load, T-cell analysis and brain histopathology. We report for the first time, disruption of excitatory amino acid transporters (EAATs), the cardinal glutamate clearing system, during SIV infection and a dramatic loss of EAATs associated with development of rapid acquired immunodeficiency syndrome (AIDS). EAATs impairment was correlated with activation status of microglia. Our data support the glutamate hypothesis for the development of HIV dementia and suggest that the pathogenetic mechanism for the neurodysfunction is the impairment of glutamate clearing which occurs in the stage of AIDS and which is associated with activated microglia.

Memantine upregulates BDNF and prevents dopamine deficits in SIV-infected macaques: a novel pharmacological action of memantine.

N-methyl-D-aspartate (NMDA) receptor activation is involved in the pathogenetic cascades of neurodegenerative disorders including human immunodeficiency virus (HIV) dementia. Memantine, an uncompetitive NMDA receptor antagonist, which has been recently approved for the treatment of Alzheimer's disease, is being discussed as a potential adjunctive therapeutic substance for HIV dementia. We used simian immunodeficiency virus-infected rhesus macaques to assess the effects of memantine on brain dysfunction and brain pathology within 3-5 months after initial infection during early asymptomatic stage of disease. We had shown previously that within this time frame, marked changes were evident in the dopaminergic systems. Memantine was administered two weeks post infection, at peak viremia, in order to prevent early NMDA receptor activation due to immune mediators. We found that memantine prevented onset of dopamine deficits in the brains of SIV-infected macaques, without affecting early brain pathology or peripheral course of infection. Memantine specifically upregulated mRNA and protein expression of the neurotrophic factor brain-derived neurotrophic factor (BDNF), suggesting that the protective effect of memantine on dopamine function may be mechanistically remote from NMDA receptor antagonism. This novel pharmacological action of memantine may also be relevant for other neurodegenerative disorders and supports the involvement of neurotrophic factors in adult brain neuroprotection.

HIV-1-associated neurocognitive disorder: epidemiology, pathogenesis, diagnosis, and treatment.

The modern antiretroviral treatment of human immunodeficiency virus (HIV-1) infection has considerably lowered the incidence of opportunistic infections. With the exception of the most severe dementia manifestations, the incidence and prevalence of HIV-associated neurocognitive disorders (HAND) have not decreased, and HAND continues to be relevant in daily clinical practice. Now, HAND occurs in earlier stages of HIV infection, and the clinical course differs from that before the widespread use of combination antiretroviral treatment (cART). The predominant clinical feature is a subcortical dementia with deficits in the domains concentration, attention, and memory. Motor signs such as gait disturbance and impaired manual dexterity have become less prominent. Prior to the advent of cART, the cerebral dysfunction could at least partially be explained by the viral load and by virus-associated histopathological findings. In subjects where cART has led to undetectable or at least very low viral load, the pathogenic virus-brain interaction is less direct, and an array of poorly understood immunological and probably toxic phenomena are discussed. This paper gives an overview of the current concepts in the field of HAND and provides suggestions for the diagnostic and therapeutic management.

Extreme phenotypic variability in a German family with X-linked myotubular myopathy associated with E404K mutation in MTM1.

X-linked myotubular myopathy (XLMTM) is a congenital muscle disorder caused by mutations in the MTM1 gene. Affected males usually present at birth with severe hypotonia and respiratory insufficiency, and most of them die within the first few years of life. We report here on a 68-year-old patient with a very mild form of the disease who was diagnosed after his grandson showed muscular weakness and respiratory problems at birth. The E404K mutation in the MTM1 gene was found in both patients. To our knowledge, this grandfather is one of the oldest and most mildly affected known patients with an MTM1 mutation to date. Thus, this family represents a remarkable phenotypic variation of XLMTM ranging from a congenital to a mild adult form.

Supracubital perineurioma misdiagnosed as carpal tunnel syndrome: case report.

BACKGROUND: Perineuriomas have been defined as tumorous lesions of the peripheral nerves which derive from perineurial cell proliferation and may be associated with abnormalities on chromosome 22. CASE PRESENTATION: Three years after a painful cubital vein procaine injection, a 33 year-old man developed a median nerve lesion, initially diagnosed as carpal tunnel syndrome. Symptoms progressed despite appropriate surgery. Clinical and electrophysiological re-evaluation revealed a fusiform mass at the distal upper arm, confirmed by MRI. Immunohistochemical studies classified the tumor as a mixed perineurioma and neuroma. CONCLUSIONS: Perineurioma mixed with neuroma may potentially caused by the previous trauma or cytotoxic effects of procaine.

Unusual multisystemic involvement and a novel BAG3 mutation revealed by NGS screening in a large cohort of myofibrillar myopathies.

BACKGROUND: Myofibrillar myopathies (MFM) are a group of phenotypically and genetically heterogeneous neuromuscular disorders, which are characterized by protein aggregations in muscle fibres and can be associated with multisystemic involvement. METHODS: We screened a large cohort of 38 index patients with MFM for mutations in the nine thus far known causative genes using Sanger and next generation sequencing (NGS). We studied the clinical and histopathological characteristics in 38 index patients and five additional relatives (n = 43) and particularly focused on the associated multisystemic symptoms. RESULTS: We identified 14 heterozygous mutations (diagnostic yield of 37%), among them the novel p.Pro209Gln mutation in the BAG3 gene, which was associated with onset in adulthood, a mild phenotype and an axonal sensorimotor polyneuropathy, in the absence of giant axons at the nerve biopsy. We revealed several novel clinical phenotypes and unusual multisystemic presentations with previously described mutations: hearing impairment with a FLNC mutation, dysphonia with a mutation in DES and the first patient with a FLNC mutation presenting respiratory insufficiency as the initial symptom. Moreover, we described for the first time respiratory insufficiency occurring in a patient with the p.Gly154Ser mutation in CRYAB. Interestingly, we detected a polyneuropathy in 28% of the MFM patients, including a BAG3 and a MYOT case, and hearing impairment in 13%, including one patient with a FLNC mutation and two with mutations in the DES gene. In four index patients with a mutation in one of the MFM genes, typical histological findings were only identified at the ultrastructural level (29%). CONCLUSIONS: We conclude that extraskeletal symptoms frequently occur in MFM, particularly cardiac and respiratory involvement, polyneuropathy and/or deafness. BAG3 mutations should be considered even in cases with a mild phenotype or an adult onset. We identified a genetic defect in one of the known genes in less than half of the MFM patients, indicating that more causative genes are still to be found. Next generation sequencing techniques should be helpful in achieving this aim.

Long-term diffusion impairment of cerebral white matter in a degenerative disease of the central and peripheral nervous system: reflection of chronic excitotoxicity?

The authors report an abnormal prolonged restricted magnetic resonance imaging (MRI) proton diffusion that persisted for more than 2 years in a 6.5-year-old boy with a progressive neurological disease characterized by developmental retardation, peripheral polyneuropathy, and bilateral optical nerve atrophy. The long-term restricted magnetic resonance imaging proton diffusion observed in diffusion-weighted magnetic resonance images indicates chronic metabolic tissue impairment in the affected white matter, whereas measurable lactate accumulation in proton magnetic resonance spectroscopy was absent, and no respiratory complex abnormality was found in muscle tissue. These findings are suggestive of a chronically disturbed regulation of energy supply triggering a "slow onset" excitotoxicity, causing chronic hypoxia and leading to slow cell death as has been postulated in certain neurodegenerative processes.

Clinical improvement precedes lesion size regression in a severe case of acute disseminated encephalomyelitis.

Here, we present a case of a severe acute disseminated encephalomyelitis (ADEM) of a 42-year-old male patient. The diagnosis was established after brain biopsy and due to acutely evolving encephalopathy occurring in the context of atypical Mycoplasma pneumoniae (MP). We analysed the prominent MRI white matter lesions using a three-dimensional algorithm as cutting-edge technique to study morphological abnormalities and correlated them to the clinical condition of the patient. We found a discrepancy between the lesion size and the clinical deficits of the patient, actually the clinical improvement antedated the regression of the white matter lesions.

Inclusion body myositis in a patient with long standing rheumatoid arthritis treated with anti-TNFalpha and rituximab.

Adult inflammatory myopathies are rare conditions. Amongst them, inclusion body myositis (IBM) is considered to be the most common acquired myopathy in adults above 50 years of age, follows a slowly progressive course, and ultimately leads to severe disability. The case of a 57-year-old patient with long standing rheumatoid arthritis (RA) who developed muscle wasting and weakness of the quadriceps femoris after initiation of anti-TNFalpha treatment is presented. Further workup including muscle biopsy revealed IBM. Initiation of rituximab for continuing synovial inflammation led to remission of RA, but no amelioration of muscle weakness was noted. Although cases of IBM in patients with autoimmune disorders have occasionally been reported and are believed to more favourably respond to immunosuppressive treatment, our patient was unresponsive to glucocorticoids. Furthermore, deterioration of muscle strength was noted with both adalimumab and etanercept treatment. Rituximab, not previously used in IBM, successfully controlled RA, but showed no effect on muscle strength. The present case underlines the therapeutic difficulties in IBM and suggests that anti-TNFalpha therapy might even be deleterious. While an early trial of the lymphocyte-depleting antibody alemtuzumab in IBM showed promising results, selective anti-B-cell-therapy remained without effect in our patient.