Search

In utero exposure to maternal antibodies targeting the fetal acetylcholine receptor isoform (fAChR) can impair fetal movement, leading to arthrogryposis multiplex congenita (AMC). fAChR antibodies have also been implicated in apparently rare, milder myopathic presentations termed fetal acetylcholine receptor inactivation syndrome (FARIS). The full spectrum associated with fAChR antibodies is still poorly understood. Moreover, since some mothers have no myasthenic symptoms, the condition is likely underreported, resulting in failure to implement effective preventive strategies. Here we report clinical and immunological data from a multicenter cohort (n = 46 cases) associated with maternal fAChR antibodies, 29 novel and 17 previously reported with novel follow-up data. Remarkably, in 50% of mothers there was no previously established MG diagnosis. All mothers (n = 30) had AChR antibodies, and where tested, against the fAChR (binding to fAChR was often much greater than that to the adAChR). Offspring death occurred in 11/46 (23.9%) cases, mainly antenatally due to termination of pregnancy prompted by severe AMC (7/46, 15.2%) or, during early infancy mainly from respiratory failure (4/46, 8.7%). Weakness, contractures, bulbar and respiratory involvement were prominent early in life, but improved gradually over time. Facial (25/34; 73.5%) and variable peripheral weakness (14/32; 43.8%), velopharyngeal insufficiency (18/24; 75%) and feeding difficulties (16/36; 44.4%) were the most common sequelae in long-term survivors. Other unexpected features included hearing loss (12/32; 37.5%), diaphragmatic paresis (5/35; 14.3%), CNS involvement (7/40; 17.5%) and pyloric stenosis (3/37; 8.1%). Oral salbutamol used empirically in 16/37 (43.2%) offspring resulted in symptom improvement in 13/16 (81.3%). Combining our series with all previously published cases, we identified 21/85 mothers treated with variable combinations of immunotherapies (corticosteroids/IVIG/PLEX) during pregnancy either for maternal MG symptom control (12/21 cases) or for fetal protection (9/21 cases). Compared to untreated pregnancies (64/85), maternal treatment resulted in a significant reduction in offspring deaths (P We conclude that presentations due to in utero exposure to maternal (fetal) AChR antibodies are more common than currently recognised and may mimic a wide range of neuromuscular disorders. Considering the wide clinical spectrum and likely diversity of underlying mechanisms, we propose Fetal Acetylcholine Receptor Antibody-related Disorder (FARAD) as the most accurate term for these presentations. FARAD is vitally important to recognise, to institute appropriate management strategies for affected offspring and to improve outcomes in future pregnancies. Oral salbutamol is a symptomatic treatment option in survivors.

Recessive mutations in the DNAJB2 gene, encoding the J-domain cochaperones DNAJB2a and DNAJB2b, have previously been reported as the genetic cause of progressive peripheral neuropathies, rarely involving pyramidal signs, parkinsonism, and myopathy. We describe here a family with the first dominantly acting DNAJB2 mutation resulting in a late-onset neuromyopathy phenotype. The c.832 T > G p.(*278Glyext*83) mutation abolishes the stop codon of the DNAJB2a isoform resulting in a C-terminal extension of the protein, with no direct effect predicted on the DNAJB2b isoform of the protein. Analysis of the muscle biopsy showed reduction of both protein isoforms. In functional studies, the mutant protein mislocalized to the endoplasmic reticulum due to a transmembrane helix in the C-terminal extension. The mutant protein underwent rapid proteasomal degradation and also increased the turnover of co-expressed wild-type DNAJB2a, potentially explaining the reduced protein amount in the patient muscle tissue. In line with this dominant negative effect, both wild-type and mutant DNAJB2a were shown to form polydisperse oligomers.

To review our diagnostic and treatment approaches concerning sporadic inclusion body myositis (sIBM) and polymyositis with mitochondrial pathology (PM-Mito), we conducted a retrospective analysis of clinical and histological data of 32 patients diagnosed as sIBM and 7 patients diagnosed as PM-Mito by muscle biopsy. Of 32 patients identified histologically as sIBM, 19 fulfilled the 2011 European Neuromuscular Center (ENMC) diagnostic criteria for “clinico-pathologically defined sIBM” at the time of biopsy. Among these, 2 patients developed sIBM after years of immunosuppressive treatment for organ transplantation. Of 11 patients fulfilling the histological but not the clinical criteria, including 3 cases with duration

Isolated cytochrome c oxidase (complex IV) deficiency is one of the most frequent respiratory chain defects in humans and is usually caused by mutations in proteins required for assembly of the complex. Mutations in nuclear-encoded structural subunits are very rare. In a patient with Leigh-like syndrome presenting with leukodystrophy and severe epilepsy, we identified a homozygous splice site mutation in COX8A, which codes for the ubiquitously expressed isoform of subunit VIII, the smallest nuclear-encoded subunit of complex IV. The mutation, affecting the last nucleotide of intron 1, leads to aberrant splicing, a frame-shift in the highly conserved exon 2, and decreased amount of the COX8A transcript. The loss of the wild-type COX8A protein severely impairs the stability of the entire cytochrome c oxidase enzyme complex and manifests in isolated complex IV deficiency in skeletal muscle and fibroblasts, similar to the frequent c.845_846delCT mutation in the assembly factor SURF1 gene. Stability and activity of complex IV could be rescued in the patient’s fibroblasts by lentiviral expression of wild-type COX8A. Our findings demonstrate that COX8A is indispensable for function of human complex IV and its mutation causes human disease.

MGME1, also known as Ddk1 or C20orf72, is a mitochondrial exonuclease found to be involved in the processing of mitochondrial DNA (mtDNA) during replication. Here, we present detailed insights on the role of MGME1 in mtDNA maintenance. Upon loss of MGME1, elongated 7S DNA species accumulate owing to incomplete processing of 5′ ends. Moreover, an 11-kb linear mtDNA fragment spanning the entire major arc of the mitochondrial genome is generated. In contrast to control cells, where linear mtDNA molecules are detectable only after nuclease S1 treatment, the 11-kb fragment persists in MGME1-deficient cells. In parallel, we observed characteristic mtDNA duplications in the absence of MGME1. The fact that the breakpoints of these mtDNA rearrangements do not correspond to either classical deletions or the ends of the linear 11-kb fragment points to a role of MGME1 in processing mtDNA ends, possibly enabling their repair by homologous recombination. In agreement with its functional involvement in mtDNA maintenance, we show that MGME1 interacts with the mitochondrial replicase PolgA, suggesting that it is a constituent of the mitochondrial replisome, to which it provides an additional exonuclease activity. Thus, our results support the viewpoint that MGME1-mediated mtDNA processing is essential for faithful mitochondrial genome replication and might be required for intramolecular recombination of mtDNA.

Sir, We read with great interest the article by Krasnianski et al . (2005) recently published in your journal. The authors report the absence of specific alterations of respiratory chain activities in skeletal muscle of patients with amyotrophic lateral sclerosis (ALS) and neurogenic atrophies (NA). While the data concerning NA patients are completely in line with our previous observations on six patients with spinal muscular atrophy and two patients with Tay–Sachs syndrome (cf. Vielhaber et al ., 1999), a considerable discrepancy exists between this report and data on ALS biopsies reported by our group (cf. Wiedemann et al ., 1998; Vielhaber et al ., 1999, 2000, 2001, 2003). To explain the contradictory findings, we would like to comment on differences in the investigated patient population and on the applied methods: 1. The ALS patients included in the study by Krasnianski et al . (2005) had a mean disease duration of 18 months (range …