Une cause inhabituelle d’hyperCKémie

Les élévations du taux de créatine-phospho-kinase (CPK), ou hyperCKémies, constituent le lot quotidien de nombreux myologues. Leur grande diversité étiologique rend les choses difficiles en pratique clinique, plus encore lorsque l’hyperCKémie est isolée. Mis à part les élévations transitoires liées à certaines circonstances facilement identifiables (naissance, traumatisme, exercice musculaire extrême, exposition aux statines) ou certains facteurs ethniques, de nombreuses maladies neuromusculaires peuvent en être à l’origine. Il s’agit en premier lieu des dystrophies musculaires progressives et des myopathies métaboliques (glycogénoses surtout). Les progrès obtenus dans l’identification des causes des hyperCKémies ont sensiblement progressé ces dernières années grâce, notamment, à l’utilisation plus large du NGS. Dans l’observation ci-dessous, l’accent est mis sur une cause rare d’hyperCKémie pour laquelle un marqueur érythrocytaire simple permet d’évoquer le diagnostic

Déficits cognitifs dans la myasthénie auto-immune : existe-t-il une participation du SNC? Revue de la littérature et implications cliniques

International audienc

Leukoencephalopathy due to variants in GFPT1- associated congenital myasthenic syndrome

Objective: To determine the molecular etiology of disease in 4 individuals from 2 unrelated families who presented with proximal muscle weakness and features suggestive of mitochondrial disease. Methods: Clinical information and neuroimaging were reviewed. Genome sequencing was performed on affected individuals and biological parents. Results: All affected individuals presented with muscle weakness and difficulty walking. In one family, both children had neonatal respiratory distress while the other family had 2 children with episodic deteriorations. In each family, muscle biopsy demonstrated ragged red fibers. MRI was suggestive of a mitochondrial leukoencephalopathy, with extensive deep cerebral white matter T2 hyperintense signal and selective involvement of the middle blade of the corpus callosum. Through genome sequencing, homozygous GFPT1 missense variants were identified in the affected individuals of each family. The variants detected (p.Arg14Leu and p.Thr151Lys) are absent from population databases and predicted to be damaging by in silico prediction tools. Following the genetic diagnosis, nerve conduction studies were performed and demonstrated a decremental response to repetitive nerve stimulation, confirming the diagnosis of myasthenia. Treatment with pyridostigmine was started in one family with favorable response. Conclusions: GFPT1 encodes a widely expressed protein that controls the flux of glucose into the hexosamine-biosynthesis pathway that produces precursors for glycosylation of proteins. GFPT1 variants and defects in other enzymes of this pathway have previously been associated with congenital myasthenia. These findings identify leukoencephalopathy as a previously unrecognized phenotype in GFPT1-related disease and suggest that mitochondrial dysfunction could contribute to this disorder.Guy Helman, Suvasini Sharma, Joanna Crawford, Bijoy Patra, Puneet Jain, Stephen J. Bent, Andoni Urtizberea, Ravindra K. Saran, Ryan J. Taft, Marjo S. van der Knaap, and Cas Simon

Mutations in the nebulin gene associated with autosomal recessive nemaline myopathy

The congenital nemaline myopathies are rare hereditary muscle disorders characterized by the presence in the muscle fibers of nemaline bodies consisting of proteins derived from the Z disc and thin filament. In a single large Australian family with an autosomal dominant form of nemaline myopathy, the disease is caused by a mutation in the α-tropomyosin gene TPM3. The typical form of nemaline myopathy is inherited as an autosomal recessive trait, the locus of which we previously assigned to chromosome 2q21.2-q22. We show here that mutations in the nebulin gene located within this region are associated with the disease. The nebulin protein is a giant protein found in the thin filaments of striated muscle. A variety of nebulin isoforms are thought to contribute to the molecular diversity of Z discs. We have studied the 3′ end of the 20.8-kb cDNA encoding the Z disc part of the 800-kDa protein and describe six disease-associated mutations in patients from five families of different ethnic origins. In two families with consanguineous parents, the patients were homozygous for point mutations. In one family with nonconsanguineous parents, the affected siblings were compound heterozygotes for two different mutations, and in two further families with one detected mutation each, haplotypes are compatible with compound heterozygosity. Immunofluorescence studies with antibodies specific to the C-terminal region of nebulin indicate that the mutations may cause protein truncation possibly associated with loss of fiber-type diversity, which may be relevant to disease pathogenesis

Eosinophilic infiltration related to CAPN3 mutations: a pathophysiological component of primary calpainopathy?

International audienceno abstrac

Implication of the SH3TC2 gene in Charcot-Marie-Tooth disease associated with deafness and/or scoliosis: Illustration with four new pathogenic variants

International audienceThe autosomal recessive demyelinating form of Charcot-Marie-Tooth can be due to SH3TC2 gene pathogenic variants (CMT4C, AR-CMTde-SH3TC2). We report on a series of 13 patients with AR-CMTde-SH3TC2 among a French cohort of 350 patients suffering from all type of inheritance peripheral neuropathy. The SH3TC2 gene appeared to be the most frequently mutated gene for demyelinating neuropathy in this series by NGS. Four new pathogenic variants have been identified: two nonsense variants (p.(Tyr970*), p.(Trp1199*)) and two missense variants (p.(Leu1126Pro), p.(Ala1206Asp)). The recurrent variant p.Arg954* was present in 62%, and seems to be a founder mutation. The phenotype is fairly homogeneous, as all these patients, except the youngest ones, presented scoliosis and/or hearing loss

Clinical and genetic heterogeneity in autosomal recessive nemaline myopathy.

Item does not contain fulltex