Facioscapulohumeral muscular dystrophy presenting isolated monomelic lower limb atrophy. Report of two patients with and without 4q35 rearrangement

Facioscapulohumeral muscular dystrophy has a distinctive regional distribution but variable clinical expression and may be markedly asymmetrical. We report two patients presenting weakness and wasting confined to a single lower limb. Creatine kinase was slightly increased, electromyogram and muscle biopsy were myopathic. Muscle computed tomography showed normal shoulder, mid-arm, pelvic and mid-thigh scans but involvement of calf muscles. In both cases, weakness of facial and periscapular muscles was found in other family members unaware of the disease. Molecular analysis showed 4q35 deletion in one family. These cases broaden the presentation of facioscapulohumeral muscular dystrophy to include isolated monomelic atrophy of lower limb with calf muscle involvement.

MERRF/MELAS overlap syndrome in a family with A3243G mtDNA mutation

Four members of a family were found to carry the A3243G mtDNA mutation. Clinical features varied from typical MELAS to myoclonic epilepsy to simple deafness without neurological signs. Several other members of the family had symptoms consistent with a mitochondrial disease. Muscle biopsy in 3 of the 4 patients showed the most prominent mitochondrial alterations with partial deficiency of cytochrome c oxidase in the case with the mildest phenotype. Mitochondrial DNA analysis detected a variable percentage of A3243G mutation, roughly correlating with the phenotype. The interesting feature of the family lies in the great intrafamilial variability of the severity of clinical expression, encompassing MELAS and MERRF features, associated with the A3243G mtDNA mutation. A search for the most common mtDNA mutations is recommended in all patients featuring incomplete MELAS or MERRF syndromes and in all familial cases presenting minimal clinical signs.

Coenzyme Q10 reverses pathological phenotype and reduces apoptosis in familial CoQ10 deficiency

Two brothers with myopathic coenzyme Q10 (CoQ10) deficiency responded dramatically to CoQ10 supplementation. Muscle biopsies before therapy showed ragged-red fibers, lipid storage, and complex I + III and II + III deficiency. Approximately 30% of myofibers had multiple features of apoptosis. After 8 months of treatment, excessive lipid storage resolved, CoQ10 level normalized, mitochondrial enzymes increased, and proportion of fibers with TUNEL-positive nuclei decreased to 10%. The authors conclude that muscle CoQ10 deficiency can be corrected by supplementation of CoQ10, which appears to stimulate mitochondrial proliferation and to prevent apoptosis.

Apoptosis and ROS detoxification enzymes correlate with cytochrome c oxidase deficiency in mitochondrial encephalomyopathies

The aim of this work was to investigate in muscle the role of apoptosis and of oxidative stress in mitochondrial disorders with dysfunction of respiratory chain. In patients with cytochrome c oxidase deficiency (COX) we found a variable number of myofibers with apoptotic nuclei that matched with the level of enzymatic reduction and roughly correlated with muscle weakness. In parallel, a positive immunostaining for apoptosis-related proteins and Mn and Cu/Zn superoxide dismutase (SOD) were mostly localized in COX-negative fibers. Moreover, glutathione peroxidase activity was increased in muscles with high number of SOD-positive myofibers and prominent apoptotic features. No signs of apoptosis were observed in patients with deficiencies of complexes I and II and without muscle weakness. These data suggest that apoptosis along with increased ROS production, revealed by anti-oxidant enzymes overexpression, may play an important role in the pathophysiology of mitochondrial diseases associated with COX deficiency.

Fine mapping of a distinctive autosomal dominant vacuolar neuromyopathy using 11 novel microsatellite markers from chromosome band 19p13.3

We previously mapped a distinctive autosomal dominant vacuolar neuromyopathy on human chromosome 19p13 in an 8cM region, delimited by D19S209 and D19S177 markers. We now report the fine mapping of the disease locus within an interval of 250 Kb by haplotype analysis performed using a set of 11 novel microsatellite markers isolated from the candidate region.

Apoptotic features accompany acute quadriplegic myopathy

OBJECTIVE

To investigate the role of apoptosis in acute quadriplegic myopathy.

BACKGROUND

Acute quadriplegic myopathy is a muscular disease characterized by diffuse flaccid weakness occurring in patients with severe systemic illness and exposure to corticosteroids or neuroblocking agents. Myofiber atrophy and thick filament loss are the distinguishing pathologic features on muscle biopsy. Increased calpains expression and lysosomal and nonlysosomal proteolytic pathways have been claimed as possible pathogenic factors. Nevertheless, the mechanisms leading to myofiber atrophy and thick filament loss need further investigation.

PATIENTS AND METHODS

The expression of ubiquitin and proapoptotic proteases as well as DNA fragmentation in muscle biopsies from three patients with acute quadriplegic myopathy were studied.

RESULTS

All patients exhibited an important overexpression of caspases, calpain, cathepsin B, and ubiquitin, and the presence of numerous apoptotic nuclei in over 70% of myofibers.

CONCLUSIONS

These data suggest that apoptosis mediated by proteolytic proteases may play a role in the pathogenesis of acute quadriplegic myopathy.

Single-fiber PCR in MELAS(3243) patients: correlations between intratissue distribution and phenotypic expression of the mtDNA(A3243G) genotype

We performed morphological, biochemical, and genetic studies, including single-fiber PCR (sf PCR), on muscle biopsies obtained from a mother and daughter with MELAS syndrome due to the A3243G transition of mitochondrial DNA (mtDNA). The severity of muscle involvement appeared quite distinct, in spite of the fact that both patients segregated similar mutant mtDNA levels on total muscle DNA. The daughter did not show any clinical muscle involvement: muscle biopsy revealed many ragged red fibers (RRFs) mostly positive for cytochrome-c oxidase (COX) activity. In contrast, her mother had developed a generalized myopathy without progressive external ophthalmoplegia (PEO), morphologically characterized by many COX-negative RRFs. Single-muscle fiber PCR demonstrated in both patients significantly higher percentages of wild-type mtDNA in normal fibers (daughter: 23.25 +/- 15.22; mother: 43.13 +/- 26.11) than in COX-positive RRFs (daughter: 11.25 +/- 5.22, P < 0.005; mother: 9.12 +/- 5.9, P < 0.001) and in COX-negative RRFs (daughter: 8.9 +/- 4.2, P < 0.001 mother: 4.8 +/- 2.8, P < 0.001). Wild-type mtDNA levels resulted higher also in COX-positive vs. COX-negative RRFs (daughter: P < 0.05; mother: P < 0.001). Our data confirm a direct correlation between A3243G levels and impairment of COX function at the single-muscle fiber level. Moreover, the evidence of a clinical myopathy in the patient with higher amounts of COX-negative RRFs bolsters the concept that a differential distribution of mutant mtDNAs at the cellular level may have effects on the clinical involvement of individual tissues. However, the occurrence of a similar morphological and biochemical muscle phenotype also in PEO(3243) patients suggests that other genetic factors involved in the interaction between mitochondrial and nuclear DNA, rather than the stochastic distribution of mtDNA genomes during embryogenesis, are primarily implicated in determining the various clinical expressions of the A3243G of mtDNA.

Hepatocellular carcinoma complicating liver cirrhosis in type IIIa glycogen storage disease

Type III glycogen storage disease (GSD III) is an autosomal recessive disorder characterized by the accumulation of abnormal glycogen in the liver and, in most patients, in the muscle. Although liver fibrosis is a well-known consequence of GSD III, until now only eight cases of liver cirrhosis and two cases of hepatocellular carcinoma have been described in patients affected by this disease. In this case report, the authors describe the clinical history of a patient affected by GSD III who developed severe liver disease during her adult life, progressing from fibrosis to cirrhosis and finally to hepatocellular carcinoma. Until now, the hepatic involvement in GSD III has been considered by most authors as mild and almost always self-limiting. This report, together with the previously published cases, clearly indicates that severe and progressive liver disease may complicate this metabolic disorder. These observations advise a careful hepatologic follow-up of patients affected by GSD III.

Gamma1- and gamma2-syntrophins, two novel dystrophin-binding proteins localized in neuronal cells

Dystrophin is the scaffold of a protein complex, disrupted in inherited muscular dystrophies. At the last 3' terminus of the gene, a protein domain is encoded, where syntrophins are tightly bound. These are a family of cytoplasmic peripheral membrane proteins. Three genes have been described encoding one acidic (alpha1) and two basic (beta1 and beta2) proteins of approximately 57-60 kDa. Here, we describe the characterization of two novel putative members of the syntrophin family, named gamma1- and gamma2-syntrophins. The human gamma1-syntrophin gene is composed of 19 exons and encodes a brain-specific protein of 517 amino acids. The human gamma2-syntrophin gene is composed of at least 17 exons, and its transcript is expressed in brain and, to a lesser degree, in other tissues. We mapped the gamma1-syntrophin gene to human chromosome 8q11 and the gamma2-syntrophin gene to chromosome 2p25. Yeast two-hybrid experiments and pull-down studies showed that both proteins can bind the C-terminal region of dystrophin and related proteins. We raised antibodies against these proteins and recognized expression in both rat and human central neurons, coincident with RNA in situ hybridization of adjacent sections. Our present findings suggest a differentiated role of a modified dystrophin-associated complex in the central nervous system.

A new mtDNA mutation associated with a progressive encephalopathy and cytochrome c oxidase deficiency

The authors describe a novel pathogenic G5540A transition in the mitochondrial transfer RNA (tRNA)Trp gene of a sporadic encephalomyopathy characterized by spinocerebellar ataxia. Clinical features also included neurosensorial deafness, peripheral neuropathy, and dementia. Biochemistry revealed a severe reduction of cytochrome c oxidase (COX) activity. Single-fiber PCR demonstrated higher levels of mutant genomes in COX-negative ragged red fibers than in normal fibers. These findings confirm that COX is more susceptible than other respiratory chain complexes to mutations in the mitochondrial tRNATrp gene.

An Italian family with autosomal recessive quadriceps-sparing inclusion-body myopathy (ARQS-IBM) linked to chromosome 9p1

We report an Italian family with autosomal recessive quadriceps-sparing inclusion-body myopathy (ARQS-IBM). The patients (two second cousins) developed a slowly progressive distal and proximal myopathy with complete sparing of the quadriceps. Muscle biopsy showed rimmed vacuoles in numerous muscle fibers, and electron microscopy documented accumulation of 15-21 nm filaments. DNA analysis established linkage to 9p1 and haplotype analysis revealed that the patients shared a recombined common haplotype. The gene locus of ARQS-IBM was initially mapped to chromosome 9p1-q1 in families of Iranian-Jewish origin and later confirmed in a few other ethnic groups. This is the first report of Italian patients with ARQS-IBM showing positive linkage to chromosome 9p1. Our data suggest that patients having distal and proximal myopathy with rimmed vacuoles and possible recessive inheritance, often classified as distal myopathies, should be thoroughly investigated according to the diagnostic criteria of h-IBM and, when positive, studied for linkage to chromosome 9p1.

GCG genetic expansions in Italian patients with oculopharyngeal muscular dystrophy

OBJECTIVE

To screen Italian patients with oculopharyngeal muscular dystrophy (OPMD) for GCG repeat expansions in the Poly(A) binding-protein 2 (PABP2) gene.

BACKGROUND

Oculopharyngeal muscular dystrophy is an adult-onset autosomal dominant muscle disease linked to 14q11 pathologically characterized by unique 8.5 nm intranuclear filaments in skeletal muscle fibers. Short expansions of a (GCG)6 repeat located in exon 1 of the newly isolated PABP2 gene have been demonstrated in a large number of OPMD families.

METHODS

We studied 18 patients diagnosed with OPMD. A muscle biopsy was performed in 16 patients. Screening for the pathologic expansion was performed on a PCR amplified DNA fragment encompassing the GCG repeat.

RESULTS

Heterozygous (GCG)-repeat expansions were detected in 13 patients in association with (GCG)6 normal allele or (GCG)7 polymorphic allele. All the patients whose muscle biopsy showed typical 8.5 nm intranuclear filaments had a mutated PABP2 allele. Five patients with no intranuclear filaments were homozygous for the normal (GCG)6 allele. The pathologic expansion appeared to be stable with no variation among family members and between different tissues as blood and skeletal muscle in the same individual.

CONCLUSIONS

These data 1) further confirm PABP2 gene analysis as a valuable tool in OPMD diagnosis; 2) indicate that PABP2 gene mutations are always present among Italian patients with morphologically proven OPMD, suggesting genetic homogeneity of the disease; and 3) strengthen the putative role of mutated PABP2 protein in filamentous inclusions accumulation.

Apoptosis in mitochondrial encephalomyopathies with mitochondrial DNA mutations: a potential pathogenic mechanism

Mitochondrial encephalomyopathies caused by mitochondrial DNA (mtDNA) defects are a genetically and phenotypically heterogeneous group of disorders. The site, percentage and distribution of mutations do not explain the overall clinical heterogeneity that is found. Apoptosis (programmed cell death) is an evolutionarily conserved mechanism that is essential for tissue development and homeostasis. Dysregulation of apoptosis has been implicated in the pathogenesis of various human diseases, such as cancer and autoimmune and neurodegenerative disorders. Recent in vitro evidence has indicated the central role of mitochondria in the apoptotic process. We investigated the occurrence of apoptosis in muscle biopsies of 36 patients carrying different mtDNA mutations and four patients with inclusion body myositis and mitochondrial abnormalities. Apoptotic features, mainly localized in cytochrome c oxidase-negative fibres, were observed in muscle fibres of patients carrying a high percentage of single mtDNA deletions (>40%) and of tRNA point mutations (>70%). By contrast, no apoptotic changes were observed in inclusion body myositis and in patients carrying mutations of mtDNA structural genes. Our study suggests that apoptosis is not simply a means whereby cells with dysfunctional mitochondria are eliminated, but that it seems to play a role in the pathogenesis of mitochondrial disorders associated with mtDNA defects affecting mitochondrial protein synthesis. The imbalance and relative abundances of nuclear-encoded and mtDNA-encoded subunits may favour cytochrome c inactivation and release. Cytochrome c, together with respiratory chain dysfunction, could activate apoptotic pathways that, in turn, inhibit the rate of mitochondrial translation and the importation of nuclear-encoded mitochondrial protein precursors. This vicious circle may amplify the biochemical defects and tissue damage and contribute to the modulation of clinical features.

A distinctive autosomal dominant vacuolar neuromyopathy linked to 19p13

OBJECTIVE

To characterize a kindred with a distinctive autosomal dominant neuromuscular disorder.

BACKGROUND

The authors studied a large Italian family affected by a progressive neuromyopathy. Ten individuals over three generations were affected. The disease was characterized by onset from the late teens to early 50s with distal leg weakness and atrophy, development of generalized muscle weakness with distal-to-proximal progression sparing facial and ocular muscles, dysphonia and dysphagia, pes cavus and areflexia, variable clinical expression ranging from subclinical myopathy to severely disabling weakness, and mixed neurogenic and myopathic abnormalities on electromyography.

METHODS

Morphologic, immunocytochemical, and ultrastructural studies were performed in muscle biopsies from three affected patients. A genomewide linkage analysis through the genotyping of 292 microsatellite markers spanning the 22 autosomes was undertaken to map the disorder segregating in this family.

RESULTS

All muscle biopsies showed variation of fiber size, panesterase-positive angular fibers, mild to severe fibrosis, and numerous "rimmed vacuoles." Electron microscopy failed to demonstrate the nuclear or cytoplasmic filamentous inclusions specific of inclusion-body myopathies and, accordingly, immunohistochemistry did not show any positivity with SMI-31 antibodies detecting hyperphosphorylated tau. Preliminary analysis of 292 microsatellite markers provided evidence for linkage to chromosome 19p13.

CONCLUSIONS

This distinctive autosomal dominant disorder is characterized by a vacuolar neuromyopathy. Localization to chromosome 19p13 will allow the genetic relationship between this disease and inherited myopathies with rimmed vacuoles, in particular autosomal dominant inclusion-body myopathies, to be defined.