C. Márquez

Redefining dysferlinopathy phenotypes based on clinical findings and muscle imaging studies

Background: The most frequent phenotypes of dysferlin myopathy are limb-girdle muscular dystrophy 2B (LGMD2B) and Miyoshi myopathy (MM). Our objective was to find clinical or MRI markers to differentiate phenotypes of dysferlin myopathy regardless of initial symptoms. Methods: This retrospective study included 29 patients with confirmed mutations in the DYSF gene (14 MM, 12 LGMD2B, 1 asymptomatic hyperCKemia, and 2 symptomatic carriers). All underwent an annual clinical examination (Medical Research Council scale), functional status assessment, and creatine kinase, pulmonary, and cardiac testing. For research purposes, we performed lower limb MRI studies in all 29 patients to identify the pattern of muscle impairment and to quantify involvement. Statistical correlations between MRI findings and phenotype, disease duration, and functional status were determined. Results: The mean clinical follow-up was 6.4 ± 5.7 years. No significant differences were found in the rate of progression, functional prognosis, or mutations between patients with MM and patients with LGMD2B. The MRI pattern of muscle involvement was the same for patients with MM and patients with LGMD2B. The adductor magnus and gastrocnemius medialis were the first to be impaired in both phenotypes. The progression of muscle involvement correlated with clinical status. Conclusions: Splitting dysferlin myopathy into separate phenotypes does not reveal significant differences in terms of rate of progression, prognosis, genotype, or MRI pattern. The finding that proximal and distal muscles are already impaired in the MRI at onset in both MM and LGMD2B favors grouping all phenotypes under the term dysferlin myopathy.

Dysferlin expression in monocytes: A source of mRNA for mutation analysis

Dysferlin protein is expressed in peripheral blood monocytes. The genomic analysis of the DYSF gene has proved to be time consuming because it has 55 exons. We designed a mutational screening strategy based on cDNA from monocytes to find out whether the mutational analysis could be performed in mRNA from a source less invasive than the muscle biopsy. We studied 34 patients from 23 families diagnosed with dysferlinopathy. The diagnosis was based on clinical findings and on the absence of protein expression using either immunohistochemistry or Western blot of skeletal muscle and/or monocytes. We identified 28 different mutations, 13 of which were novel. The DYSF mutations in both alleles were found in 30 patients and only in one allele in four. The results were confirmed using genomic DNA in 26/34 patients. This is the first report to furnish evidence of reliable mutational analysis using monocytes cDNA and constitutes a good alternative to genomic DNA analysis.

Acute paraparesis following intravenous steroid therapy in a case of dural spinal arteriovenous fistula

JO N 2 94 3 tion showed symmetric iliopsoas weakness (manual muscular balance 4+/5), few fasciculations in left quadriceps, and stocking type distribution of hypoesthesia. Knee and ankle reflexes were absent. Plantar reflex was neutral. The patient was unstable when standing upright with eyes closed. Electroneurography and electromyography were normal. A lumbar puncture, performed on the first day of hospitalization, showed cerebrospinal fluid containing one leukocyte, eight red blood cells, 60 mg/dl of proteins and 46 mg/dl of glucose. A lumbar MRI showed an enlargement of the conus medullaris, with an area of T2 hyperintensity and gadolinium enhancement suggesting an inflammatory or a neoplasic process affecting the spine. Then, on the seventh day of hospitalization, methylprednisolone was prescribed at doses of 1 g endovenous daily diluted in 500 ml of saline solution, over five days. The first day of treatment, two hours after finishing the bolus, the patient complained Macarena Cabrera Carmen Paradas Celedonio Márquez Alejandro González

Junctophilin-1 is a modifier gene of GDAP1-related Charcot–Marie–Tooth disease

Mutations in the GDAP1 gene cause different forms of Charcot-Marie-Tooth (CMT) disease, and the primary clinical expression of this disease is markedly variable in the dominant inheritance form (CMT type 2K; CMT2K), in which carriers of the GDAP1 p.R120W mutation can display a wide range of clinical severity. We investigated the JPH1 gene as a genetic modifier of clinical expression variability because junctophilin-1 (JPH1) is a good positional and functional candidate. We demonstrated that the JPH1-GDAP1 cluster forms a paralogon and is conserved in vertebrates. Moreover, both proteins play a role in Ca(2+) homeostasis, and we demonstrated that JPH1 is able to restore the store-operated Ca(2+) entry (SOCE) activity in GDAP1-silenced cells. After the mutational screening of JPH1 in a series of 24 CMT2K subjects who harbour the GDAP1 p.R120W mutation, we characterized the JPH1 p.R213P mutation in one patient with a more severe clinical picture. JPH1(p.R213P) cannot rescue the SOCE response in GDAP1-silenced cells. We observed that JPH1 colocalizes with STIM1, which is the activator of SOCE, in endoplasmic reticulum-plasma membrane puncta structures during Ca(2+) release in a GDAP1-dependent manner. However, when GDAP1(p.R120W) is expressed, JPH1 seems to be retained in mitochondria. We also established that the combination of GDAP1(p.R120W) and JPH1(p.R213P) dramatically reduces SOCE activity, mimicking the effect observed in GDAP1 knock-down cells. In summary, we conclude that JPH1 and GDAP1 share a common pathway and depend on each other; therefore, JPH1 can contribute to the phenotypical consequences of GDAP1 mutations.

Mitochondrial DNA polymorphisms/haplogroups in hereditary spastic paraplegia

Mitochondrial dysfunction could contribute to the development of spastic paraplegia. Among others, two of the genes implicated in hereditary spastic paraplegia encoded mitochondrial proteins and some of the clinical features frequently found in these patients resemble those observed in patients with mitochondrial DNA (mtDNA) mutations. We investigated the association between common mtDNA polymorphisms and spastic paraplegia. The ten mtDNA polymorphisms that defined the common European haplogroups were determined in 424 patients, 19% with a complicated phenotype. A rare haplogroup was associated with the disease in patients without a SPG3A, SPG4, or SPG7 mutation. Allele 10398G was more frequent among patients with a pure versus complicated phenotype. This mtDNA polymorphism was previously associated with the risk of developing other neurodegenerative diseases. In conclusion, some mtDNA polymorphisms could contribute to the development of spastic paraplegia or act as modifiers of the phenotype.

Antidisialosyl antibodies in chronic idiopathic ataxic neuropathy

Abstract. Antidisialosyl antibodies were found in two out of 13 patients with chronic idiopathic ataxic neuropathy (CIAN) and not in 32 patients with different sensory neuropathies of known cause. This finding confirms the association of antidisialosyl antibodies and CIAN regardless of the absence of the M band. These antibodies may have pathogenic relevance; however, larger series are needed to establish their clinical significance.

X-linked Emery–Dreifuss muscular dystrophy and vacuoles: An immunohistochemical characterization

We report a striking abundance of rimmed vacuoles in two brothers with X‐linked Emery–Dreifuss muscular dystrophy (X‐EDMD) confirmed by the absence of emerin at the muscular nuclear envelope and by genetic analysis showing a new 2‐bp deletion in exon 6 of the STA gene at the Xq28 region. Immunohistochemical analysis of the vacuoles revealed expression of dystrophin but not of merosin in the sarcolemma of rimmed vacuoles and absence of amyloid and membrane attack complex (MAC) deposition either in vacuoles or muscle fibers. The presence of rimmed vacuoles can be a histopathological finding in X‐EDMD, and the diagnosis should not be excluded in clinically well‐defined EDMD patients because of this finding. Muscle Nerve, 2005