Dataset Information

Clinical, histological, and genetic characterization of PYROXD1-related myopathy.

ABSTRACT: Recessive mutations in PYROXD1, encoding an oxidoreductase, were recently reported in families with congenital myopathy or limb-girdle muscular dystrophy. Here we describe three novel PYROXD1 families at the clinical, histological, and genetic level. Histological analyses on muscle biopsies from all families revealed fiber size variability, endomysial fibrosis, and muscle fibers with multiple internal nuclei and cores. Further characterization of the structural muscle defects uncovered aggregations of myofibrillar proteins, and provided evidence for enhanced oxidative stress. Sequencing identified homozygous or compound heterozygous PYROXD1 mutations including the first deep intronic mutation reinforcing a cryptic donor splice site and resulting in mRNA instability through exonisation of an intronic segment. Overall, this work expands the PYROXD1 mutation spectrum, defines and specifies the histopathological hallmarks of the disorder, and indicates that oxidative stress contributes to the pathomechanism. Comparison of all new and published cases uncovered a genotype/phenotype correlation with a more severe and early-onset phenotypic presentation of patients harboring splice mutations resulting in reduced PYROXD1 protein levels compared with patients carrying missense mutations.

SUBMITTER: Lornage X

PROVIDER: S-EPMC6710884 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature

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Clinical, histological, and genetic characterization of PYROXD1-related myopathy.

Lornage Xavière X Schartner Vanessa V Balbueno Inès I Biancalana Valérie V Willis Tracey T Echaniz-Laguna Andoni A Scheidecker Sophie S Quinlivan Ros R Fardeau Michel M Malfatti Edoardo E Lannes Béatrice B Sewry Caroline C Romero Norma B NB Laporte Jocelyn J Böhm Johann J Böhm Johann J

Acta neuropathologica communications 20190827 1

Recessive mutations in PYROXD1, encoding an oxidoreductase, were recently reported in families with congenital myopathy or limb-girdle muscular dystrophy. Here we describe three novel PYROXD1 families at the clinical, histological, and genetic level. Histological analyses on muscle biopsies from all families revealed fiber size variability, endomysial fibrosis, and muscle fibers with multiple internal nuclei and cores. Further characterization of the structural muscle defects uncovered aggregati ...[more]

PMID: 31455395

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Project description:We recently identified the X-chromosomal four and a half LIM domain gene FHL1 as the causative gene for reducing body myopathy, a disorder characterized by progressive weakness and intracytoplasmic aggregates in muscle that exert reducing activity on menadione nitro-blue-tetrazolium (NBT). The mutations detected in FHL1 affected highly conserved zinc coordinating residues within the second LIM domain and lead to the formation of aggregates when transfected into cells. Our aim was to define the clinical and morphological phenotype of this myopathy and to assess the mutational spectrum of FHL1 mutations in reducing body myopathy in a larger cohort of patients. Patients were ascertained via the detection of reducing bodies in muscle biopsy sections stained with menadione-NBT followed by clinical, histological, ultrastructural and molecular genetic analysis. A total of 11 patients from nine families were included in this study, including seven sporadic patients with early childhood onset disease and four familial cases with later onset. Weakness in all patients was progressive, sometimes rapidly so. Respiratory failure was common and scoliosis and spinal rigidity were significant in some of the patients. Analysis of muscle biopsies confirmed the presence of aggregates of FHL1 positive material in all biopsies. In two patients in whom sequential biopsies were available the aggregate load in muscle sections appeared to increase over time. Ultrastructural analysis revealed that cytoplasmic bodies were regularly seen in conjunction with the reducing bodies. The mutations detected were exclusive to the second LIM domain of FHL1 and were found in both sporadic as well as familial cases of reducing body myopathy. Six of the nine mutations affected the crucial zinc coordinating residue histidine 123. All mutations in this residue were de novo and were associated with a severe clinical course, in particular in one male patient (H123Q). Mutations in the zinc coordinating residue cysteine 153 were associated with a milder phenotype and were seen in the familial cases in which the boys were still more severely affected compared to their mothers. We expect the mild end of the spectrum to significantly expand in the future. On the severe end of the spectrum we define reducing body myopathy as a progressive disease with early, but not necessarily congenital onset, distinguishing this condition from the classic essentially non-progressive congenital myopathies.

Dataset Information

Clinical, histological, and genetic characterization of PYROXD1-related myopathy.

Publications

Clinical, histological, and genetic characterization of PYROXD1-related myopathy.

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