Myocardial strain analysis using cardiac magnetic resonance in patients with calpainopathy.

BACKGROUND: Limb-girdle muscular dystrophy (LGMD) is a genetically and clinically heterogeneous group of rare muscular dystrophies. Subtype 2A (LGMD2A) also known as "calpainopathy" is an inherited autosomal recessive gene defect. Cardiac dysfunction is common in several forms of LGMD. Cardiac involvement in LGMD2A, however, is not clear. The aim of this study was to perform cardiac magnetic resonance (CMR)-based strain analysis in LGMD2A patients, as this is a diagnostic parameter of subclinical cardiac involvement and a powerful independent predictor of mortality. We conducted the largest prospective cardiac magnetic resonance study to date, including 11 genetically verified LGMD2A patients and 11 age- and sex-matched control subjects and performed CMR-based strain analysis of the left and right ventricles. RESULTS: Left and right global longitudinal strain (GLS) were not significantly different between the two groups and within normal reference ranges (left ventricle: control - 21.8 (5.1) % vs. patients - 22.3 (3.2) %, p = 0.38; right ventricle: control - 26.3 (7.2) % vs. patients - 26.8 (5.8) %, p = 0.85). Also, global circumferential and radial strains did not significantly differ between the two groups (p = 0.95 and p = 0.86, respectively). LGMD2A patients did not show relevant amounts of late gadolinium enhancement (LGE) or malignant ventricular arrhythmias. CONCLUSIONS: No evidence of even subtle cardiac dysfunction is evident form CMR-based strain analysis in LGMD2A patients. Malignant ventricular arrhythmias were not detected. Thus, in case of non-pathological initial echocardiographic and electrocardiographic examination, a less frequent or even no cardiac follow-up may be acceptable in these patients. However, if there are signs and symptoms that suggest an underlying cardiac condition (e.g. palpitations, angina, shortness of breath), this approach needs to be individualized to account for the unknown.

A case of recurrent herpes simplex 2 encephalitis, VZV reactivations, and dominant partial interferon-gamma-receptor-1 deficiency supports relevance of IFNgamma for antiviral defense in humans.

BACKGROUND: Unlike infections with mycobacteria, reports of unusual viral infections in interferon-gamma-receptor (IFNγR) deficient patients are scarce. Therefore, discussion about increased susceptibility to viral infections in these patients is ongoing. CASE PRESENTATION: We describe a 51-year-old male with dominant partial interferon-gamma-receptor-1 (IFNγR1)-deficiency and recurrent Herpes simplex 2 meningoencephalitis as well as other viral reactivations since childhood. CONCLUSIONS: This case further confirms an enhanced risk for viral disease in IFNγR-deficient patients and a role of interferon gamma for human antiviral defense.

Novel NAXE variants as a cause for neurometabolic disorder: implications for treatment.

Neurometabolic disorders are often inherited and complex disorders that result from abnormalities of enzymes important for development and function of the nervous system. Recently, biallelic mutations in NAXE (APOA1BP) were found in patients with an infantile, lethal, neurometabolic disease. Here, exome sequencing was performed in two affected sisters and their healthy parents. The best candidate, NAXE, was tested for replication in exome sequencing data from 4351 patients with neurodevelopmental disorders. Quantitative RT-PCR, western blot and form factor analysis were performed to assess NAXE expression, protein levels and to analyze mitochondrial morphology in fibroblasts. Vitamin B3 was administered to one patient. Compound heterozygous missense (c.757G>A: p.Gly253Ser) and splicing (c.665-1G>A) variants in NAXE were identified in both affected sisters. In contrast to the previously reported patients with biallelic NAXE variants, our patients showed a milder phenotype with disease onset in early adulthood with psychosis, cognitive impairment, seizures, cerebellar ataxia and spasticity. The symptoms fluctuated. Additional screening of NAXE identified three novel homozygous missense variants (p.Lys245Gln, p.Asp218Asn, p.Ile214Val) in three patients with overlapping phenotype (fluctuating disease course, respiratory insufficiency, movement disorder). Lastly, patients with the c.665-1G>A splicing variant showed a significant reduction of NAXE expression compared to control fibroblasts and undetectable NAXE protein levels compared to control fibroblasts. Based on the metabolic pathway, vitamin B3 and coenzyme Q treatment was introduced in one patient in addition to antiepileptic treatment. This combination and avoidance of triggers was associated with continuous motor and cognitive improvement. The NAXE variants identified in this study suggest a loss-of-function mechanism leading to an insufficient NAD(P)HX repair system. Importantly, symptoms of patients with NAXE variants may improve with vitamin B3/coenzyme Q administration.

Novel mutations in MYBPC1 are associated with myogenic tremor and mild myopathy.

OBJECTIVE: To define a distinct, dominantly inherited, mild skeletal myopathy associated with prominent and consistent tremor in two unrelated, three-generation families. METHODS: Clinical evaluations as well as exome and panel sequencing analyses were performed in affected and nonaffected members of two families to identify genetic variants segregating with the phenotype. Histological assessment of a muscle biopsy specimen was performed in 1 patient, and quantitative tremor analysis was carried out in 2 patients. Molecular modeling studies and biochemical assays were performed for both mutations. RESULTS: Two novel missense mutations in MYBPC1 (p.E248K in family 1 and p.Y247H in family 2) were identified and shown to segregate perfectly with the myopathy/tremor phenotype in the respective families. MYBPC1 encodes slow myosin binding protein-C (sMyBP-C), a modular sarcomeric protein playing structural and regulatory roles through its dynamic interaction with actin and myosin filaments. The Y247H and E248K mutations are located in the NH2 -terminal M-motif of sMyBP-C. Both mutations result in markedly increased binding of the NH2 terminus to myosin, possibly interfering with normal cross-bridge cycling as the first muscle-based step in tremor genesis. The clinical tremor features observed in all mutation carriers, together with the tremor physiology studies performed in family 2, suggest amplification by an additional central loop modulating the clinical tremor phenomenology. INTERPRETATION: Here, we link two novel missense mutations in MYBPC1 with a dominant, mild skeletal myopathy invariably associated with a distinctive tremor. The molecular, genetic, and clinical studies are consistent with a unique sarcomeric origin of the tremor, which we classify as "myogenic tremor." ANN NEUROL 2019.

Practically applicable nerve ultrasound models for the diagnosis of axonal and demyelinating hereditary motor and sensory neuropathies (HMSN).

PURPOSE: To develop specific diagnostic ultrasound (US) models for hereditary motor and sensory neuropathies (HMSN) in patients with primarily demyelinating or axonal polyneuropathies (PNP) according to standard nerve conduction studies (NCS) criteria. METHODS: Single-centre, examiner-blinded cross-sectional study in acquired PNP (consecutive recruitment strategy) and HMSN patients (convenience sample). Allocation into demyelinating or axonal phenotype via easily applicable NCS criteria. Assessment of single measurements by receiver-operating curve (ROC) analysis, development of diagnostic models based on the best measurement values in ROC. RESULTS: Of 85 enrolled subjects, 53 (62%) had HMSN and 32 (38%) acquired PNPs, and 60 subjects (71%) had demyelinating and 25 (29%) axonal PNP. ROC area under the curve of means of the z-transformed 5 best measurement values was 0.87 for demyelinating and 0.99 for axonal HMSN. Diagnostic models showed high accuracy for both demyelinating (84% sensitivity, 86% specificity) and axonal HMSN (100% sensitivity and specificity). As a measure of variability of morphologic changes, standard deviations of z-transformed measurements were compared for acquired PNP and HMSN. In contrast to previous reports of more homogenous nerve enlargements in HMSN, standard deviations were higher in HMSN than in acquired PNP. Additionally, the performance of previously published models for the diagnosis of HMSN in demyelinating PNP was compared. Previously published models showed lower sensitivities (50-58%), but comparable specificities (91-100%) when applied to NCS-criteria defined demyelinating PNP group. CONCLUSION: Diagnostic ultrasound models for HMSN in patients with demyelinating or axonal neuropathies show high accuracy and can contribute to differential diagnosis in clinical routine.

Diagnostic accuracy of nerve ultrasound in hereditary and sporadic non-entrapment neuropathies.

The objective of this study is to compare the diagnostic accuracy of nerve ultrasound (US) and nerve conduction studies (NCS) for acquired non-entrapment peripheral neuropathies (PNP) and hereditary motor and sensory neuropathies (HMSN) in a routine clinical setting. The methods are based on a single-center, prospective, examiner-blinded cross-sectional study on three subject groups of healthy controls, PNP (both enrolled by a consecutive recruitment strategy), and HMSN patients (convenience sample). A clinical reference standard based on the neuropathy impairment (NIS) and neuropathy symptoms scores (NSS) was used for PNP as the external validation criterion. Diagnostic accuracy was assessed by receiver-operating curve (ROC) analyses of single-nerve measurements and logit models. Of a total of 676 consecutively screened subjects, 107 (15.8 %) were recruited, of which 36 (33.6 %) had a PNP. HMSN group consisted of 53 subjects (30 subjects (56.6 %) with genetic confirmation). AUCs of best diagnostic logit models to distinguish between controls and PNP patients were 0.86 for US and 0.97 for NCS corresponding to an equivalent specificity [US 93 % (95 % CI: 83-98 %), NCS 89 % (95 % CI: 78-95 %)], but inferior sensitivity of US [US 56 % (95 % CI: 35-74 %), NCS 97 % (95 % CI: 84-100 %)]. For differentiation between PNP and HMSN, both methods had equivalent AUCs of 0.95 corresponding to similar sensitivities/specificities. Simpler diagnostic models based on measurement protocols feasible for clinical routine revealed similar diagnostic accuracies. US has an inferior sensitivity than NCS for acquired PNP, but comparable specificity. For identification of HMSN in a PNP population, US and NCS show comparable performance.

Expanded phenotypic spectrum of the m.8344A>G "MERRF" mutation: data from the German mitoNET registry.

The m.8344A>G mutation in the MTTK gene, which encodes the mitochondrial transfer RNA for lysine, is traditionally associated with myoclonic epilepsy and ragged-red fibres (MERRF), a multisystemic mitochondrial disease that is characterised by myoclonus, seizures, cerebellar ataxia, and mitochondrial myopathy with ragged-red fibres. We studied the clinical and paraclinical phenotype of 34 patients with the m.8344A>G mutation, mainly derived from the nationwide mitoREGISTER, the multicentric registry of the German network for mitochondrial disorders (mitoNET). Mean age at symptom onset was 24.5 years ±10.9 (6-48 years) with adult onset in 75 % of the patients. In our cohort, the canonical features seizures, myoclonus, cerebellar ataxia and ragged-red fibres that are traditionally associated with MERRF, occurred in only 61, 59, 70, and 63 % of the patients, respectively. In contrast, other features such as hearing impairment were even more frequently present (72 %). Other common features in our cohort were migraine (52 %), psychiatric disorders (54 %), respiratory dysfunction (45 %), gastrointestinal symptoms (38 %), dysarthria (36 %), and dysphagia (35 %). Brain MRI revealed cerebral and/or cerebellar atrophy in 43 % of our patients. There was no correlation between the heteroplasmy level in blood and age at onset or clinical phenotype. Our findings further broaden the clinical spectrum of the m.8344A>G mutation, document the large clinical variability between carriers of the same mutation, even within families and indicate an overlap of the phenotype with other mitochondrial DNA-associated syndromes.

Nerve ultrasound in the differentiation of multifocal motor neuropathy (MMN) and amyotrophic lateral sclerosis with predominant lower motor neuron disease (ALS/LMND).

The objective of the study was to investigate nerve ultrasound (US) in comparison to nerve conduction studies (NCS) for differential diagnosis of amyotrophic lateral sclerosis with predominant lower motoneuron disease(ALS/LMND) and multifocal motor neuropathy(MMN). A single-center, prospective, examiner-blinded cross-sectional diagnostic study in two cohorts was carried out. Cohort I: convenience sample of subjects diagnosed with ALS/LMND or MMN (minimal diagnostic criteria:possible ALS (revised EL-Escorial criteria), possible MMN (European Federation of Neurosciences guidelines).Cohort II: consecutive subjects with suspected diagnosis of either ALS/LMND or MMN. Diagnostic US and NCS models were developed based on ROC analysis of 28 different US and 32 different NCS values measured in cohort I. Main outcome criterion was sensitivity/specificity of these models between ALS/LMND and MMN in cohort II.Cohort I consisted of 16 patients with ALS/LMND and 8 patients with MMN. For cohort II, 30 patients were recruited, 8 with ALS/LMND, 5 with MMN, and 17 with other diseases. In cohort I, the three best US measures showed higher mean ± SD areas under the curve than the respective NCS measures (0.99 ± 0.01 vs. 0.79 ± 0.03, p<0.001; two-sided t test). The US model with highest measurement efficacy (8 values) and diagnostic quality reached 100 % sensitivity and 92 % specificity for MMN in cohort II, while the respective NCS model (6 values, including presence of conduction blocks) reached 100 and 52 %. Nerve US is of high diagnostic accuracy for differential diagnosis of ALS/LMND and MMN. It might be superior to NCS in the diagnosis of MMN in hospital-admitted patients with this differential diagnosis.

In vitro myogenic differentiation of human bone marrow-derived mesenchymal stem cells as a potential treatment for urethral sphincter muscle repair.

To explore a new treatment strategy for urinary incontinence, human bone marrow mesenchymal stem cells (MSC) of the first in vitro passage were exposed to 5-azacytidine (AZA) to induce myogenic differentiation, and cultured for a total of six passages. Expression of stem cell surface antigens and intracellular alpha-actin was examined by flow cytometry at the end of each passage and compared to that of native MSC (not exposed to AZA) cultured in parallel. To analyze differentiation into striated muscle, expression of the transcription factor MyoD1 and myosin heavy chain (MyHC) was examined by RT-PCR. Both native and AZA-exposed MSC of all passages were negative for the progenitor/endothelial antigen CD34, leukocytic CD45, and endothelial/monocytic CD31. In contrast, the MSC markers CD73, CD90, CD105, and intracellular actin were detected in both groups of MSC throughout the culture period. After an initial increase, the expression level of MSC antigens decreased over time particularly in AZA-exposed MSC. Expression of smooth muscle alpha-actin also declined, but was greater in AZA-exposed MSC throughout the culture period. Varying percentages of MSC cultures expressed MyoD1 and MyHC mRNA. In late passages, AZA-exposed MSC tended to be more frequently positive than native MSC. In pilot experiments, transplantation of MSC into the bladder neck tissue of athymic rats was feasible; long-term analyses are pending. We conclude that independent of AZA exposure, MSC express smooth and striated muscle antigens. Treatment with AZA slightly increases myogenic differentiation, but may not be necessary in future studies of MSC as a treatment modality for urinary incontinence.

Expression and localization of nuclear proteins in autosomal-dominant Emery-Dreifuss muscular dystrophy with LMNA R377H mutation.

BACKGROUND: The autosomal dominant form of Emery-Dreifuss muscular dystrophy (AD-EDMD) is caused by mutations in the gene encoding for the lamins A and C (LMNA). Lamins are intermediate filament proteins which form the nuclear lamina underlying the inner nuclear membrane. We have studied the expression and the localization of nuclear envelope proteins in three different cell types and muscle tissue of an AD-EDMD patient carrying a point mutation R377H in the lamin A/C gene. RESULTS: Lymphoblastoid cells, skin fibroblasts, primary myoblasts and muscle thin sections were studied by immunocytochemistry and electron microscopy. Cellular levels of A-type lamins were reduced compared to control cells. In contrast, the amount of emerin and lamin B appeared unaltered. Cell synchronization experiments showed that the reduction of the cellular level of A-type lamin was due to instability of lamin A. By electron microscopy, we identified a proportion of nuclei with morphological alterations in lymphoblastoid cells, fibroblasts and mature muscle fibres. Immunofluorescence microscopy showed that a major population of the lamin B receptor (LBR), an inner nuclear membrane protein, was recovered in the cytoplasm in association with the ER. In addition, the intranuclear organization of the active form of RNA polymerase II was markedly different in cells of this AD-EDMD patient. This aberrant intranuclear distribution was specifically observed in muscle cells where the pathology of EDMD predominates. CONCLUSIONS: From our results we conclude: Firstly, that structural alterations of the nuclei which are found only in a minor fraction of lymphoblastoid cells and mature muscle fibres are not sufficient to explain the clinical pathology of EDMD; Secondly, that wild type lamin A is required not only for the retention of LBR in the inner nuclear membrane but also for a correct localization of the transcriptionally active RNA pol II in muscle cells. We speculate that a rearrangement of the internal chromatin could lead to muscle-specific disease symptoms by interference with proper mRNA transcription.

Mitochondrial cytopathies.

Mitochondrial cytopathies represent a heterogeneous group of multisystem disorders which preferentially affect the muscle and nervous systems. They are caused either by mutations in the maternally inherited mitochondrial genome, or by nuclear DNA-mutations. Today, approximately 200 different disease causing mutations of mitochondrial DNA (mtDNA) are known, and due to the increased knowledge about nuclear genetics during the last few years, more and more nuclear mutations are being described. Owing to the non-uniform distribution of mitochondria in tissues and the co-existence of mutated and wildtype mtDNA (heteroplasmy) in these organelles, these disorders may present with a huge variety of symptoms, even if the same mutation is involved. Diagnostic investigations should include the measurement of serum and CSF lactate, neuroradiological tests and a muscle biopsy to show the characteristic ragged-red fibres and cytochrome c oxidase deficient cells and also to provide material for genetic analysis. To date, the treatment of these diseases remains supportive and should focus on typical complications such as cardiac dysrhythmia and endocrinopathy.