Distal Myopathy With Rimmed Vacuoles Patients Research Articles

Distal myopathy with rimmed vacuoles: Spectrum of GNE gene mutations in seven Chinese patients

Distal myopathy with rimmed vacuoles (DMRV) is a rare, autosomal, recessive inherited disease caused by mutations in the GNE gene. DMRV is an adult-onset disorder characterized by progressive muscle atrophy and weakness, which initially involves the distal muscles with quadriceps sparing. To date, >150 GNE mutations have been reported in different populations from around the world. The present study investigated the clinical, pathological and genetic characteristics of seven unrelated DMRV patients from China. Genetic analysis in these patients revealed three novel mutations (c.455_456insC, p.P421L, and p.A287T) and five previously reported mutations (p.D207V, p.C44S, p.G576R, p.A669P, and p.D218G). In addition, the literature on DMRV was reviewed to provide an overview of the disease and broaden the mutational spectrum of the GNE gene in China.

Distal myopathy with rimmed vacuoles: clinical and muscle morphological characteristics and spectrum of GNE gene mutations in 53 Chinese patients

Objectives: Distal myopathy with rimmed vacuoles (DMRV) is a typical autosomal recessive hereditary inclusion body myopathy, characterized by slowly progressive distal muscle weakness with relative sparing of the quadriceps. This study aimed to investigate the variability of clinical and morphological presentation and the spectrum of Glucosamine (UDP-N-acetyl)-2-epimerase/N-acetylmannosamine kinase (GNE) mutations in Chinese DMRV patients.Methods: We retrospectively reviewed the medical records of 37 patients with DMRV in PLA General Hospital from 1986 to 2011, and further conducted a review of 16 reported Chinese DMRV patients from other hospitals. We systematically analyzed the clinical, muscle morphological features and GNE gene mutation status of all DMRV patients.Results: A total of 53 DMRV patients were studied. Fourteen cases had family history and other 39 cases were sporadic. Fifteen cases showed atypical pathological presentation as mononuclear cell invasion into necrotic or non-necrotic muscle fibers. Rare initial symptom, earlier age of onset and more dysmorphic presentations were shown in sporadic patients. Eighteen mutations in GNE gene were identified. c.317T>C (p.I106T) was a novel GNE gene mutation. c.1892C>T (p.A631V), c.527A>T (p.D176V) and c.1523T>C (p.L508S) were the common GNE mutations in Chinese DMRV patients.Discussion: The clinical, pathological and genetic characteristics of DMRV are distinct in Chinese patients.

Clinical and molecular genetic analysis in Chinese patients with distal myopathy with rimmed vacuoles

Distal myopathy with rimmed vacuoles (DMRVs) is an autosomal recessive vacuolar myopathy that has been reported in different ethnic populations with the common mutations of UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) gene. We presented the clinical, pathological and genetic characteristics of eight Chinese DMRV patients from six unrelated families. Six previously reported Chinese DMRV patients from four unrelated families were also reviewed for comparison in GNE mutations. In the present eight patients with DMRV, direct sequencing analysis revealed one homozygous mutation of c.1760T>C (p.I587T) and seven compound heterozygous mutations in the GNE gene. The latter included two known mutations, c.1892C>T (p.A631V) and c.527A>T (p.D176V), and three novel mutations, c.1523T>C (p.L508S), c.103G>A (p.E35K) and c.153A>G (p.I51M). The allelic frequency of c.1523T>C (p.L508S) was 25% in the Chinese patients with DMRV. Our findings expand the genetic spectrum of DMRV and indicate that the common mutations of GNE gene in DMRV may be variable among different ethnic populations.

P2.04 DMRV and GNE mutations: genotype–phenotype correlation in 100 Japanese patients

Background: Distal myopathy with rimmed vacuoles (DMRV) is an autosomal recessive disorder with preferential involvement of the distal muscles in lower extremities at young adulthood and spares quadriceps muscles. In DMRV patients, we previously identified homogeneous and compound heterozygous mutations in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) gene that is the causative gene in hereditary inclusion body myopathy (hIBM). Purpose: To investigate the correlation between phenotypes and genotypes in DMRV, we analyzed the information of 100 cases of this disease in Japan.

Distal myopathy with rimmed vacuoles: Report on clinical characteristics in 23 cases

Distal myopathy with rimmed vacuoles (DMRV) is an autosomal recessive (AR) myopathy characterized clinically by the preferential involvement of the tibialis anterior and has been reported predominantly in the Japanese population. A case series of DMRV patients seen over a period of 3 years at a tertiary national referral center for neurological disorders in south India. We describe the clinical characteristics, muscle magnetic resonance imaging (MRI) findings and classical histopathological feature in 23 patients. There were 12 men and 11 women. Mean age of onset was 27.04 +/- 6.35 years (10-39 years). Onset was in the second or third decade in a majority. Mean age at presentation was 33.95 +/- 6.35 years (25-48 years). Mean duration of illness was 6.74 +/- 4.8 years (1-18 years). Consanguinity was reported in eight (34.8%) patients. The predominant and initial manifestation was bilateral foot drop in all patients. Muscle MRI demonstrated classical involvement of the anterior compartment muscles of the lower legs and the posterior compartment muscles of the thighs and the quadriceps was normal in all. Muscle histopathology showed numerous fibers containing rimmed vacuoles. Necrotic fibers or phagocytosis or regenerating fibers were rarely noted or were absent. DMRV is a rare AR myopathy. The disorder presents as progressive foot drop and hence has many differential diagnoses. It is easily mistaken as neuropathy of hereditary nature and hence it is extremely important to recognize the preferential muscle involvement and characterize the phenotype. This is the first report from India with patients having characteristic phenotype of Nonaka's/AR hereditary inclusion body myopathy with quadriceps sparing, and all were confirmed by histopathology.

Muscle weakness correlates with muscle atrophy and precedes the development of inclusion body or rimmed vacuoles in the mouse model of DMRV/hIBM

Distal myopathy with rimmed vacuoles (DMRV), also called hereditary inclusion body myopathy (hIBM), is characterized clinically by weakness and atrophy that initially involves the distal muscles and pathologically by the presence of rimmed vacuoles (RVs) or intracellular protein deposits in myofibers. It is caused by mutations in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) gene that is important in sialic acid synthesis. Recently, we generated a mouse model (Gne(-/-)hGNED176VTg) that exhibits muscle weakness and pathological changes similar to DMRV patients. To gain better understanding of the pathomechanism of DMRV, we determined temporal changes in the overall motor performance of this model mouse for DMRV in correlation with the structure and function of isolated skeletal muscles and muscle pathology. These DMRV mice exhibited muscle weakness, decreased whole muscle mass and cross-sectional area (CSA), and reduced contractile power in an age-related manner. Single-fiber CSA further supported the finding of muscle atrophy that involved both type I and type II fibers. These results suggest that atrophy is highly correlated with reduced production of force at young age, both in vivo and ex vivo, thereby implicating the important role of atrophy in the pathomechanism of DMRV. In older age, and particularly in gastrocnemius muscles, RVs and intracellular inclusions were seen in type IIA fibers, further aggravating reduction of force and specific increase in twitch-tetanus ratio.

Clinical and pathological features and prognosis of Chinese patients with distal myopathy with rimmed vacuoles: study of 17 cases

To clarify the clinical and pathological features and prognosis of Chinese patients with distal myopathy with rimmed vacuoles (DMRV). The clinical data of 17 Chinese DMRV patients with the courses of disease of 1-21 years, 5 males and 12 females, aged 28.9 (19-41), were collected. Biopsy of muscle specimens of 17 Chinese DMRV patients were summarized retrospectively. Muscle specimens were collected from the biceps brachii, tibialis anterior, gastrocnemius, or quadriceps femoris and underwent light microscopy. Eight muscle specimens underwent electron microscopy. 11 patients were followed up for 4 months to 15 years. The age of onset ranged from 5 to 40 years (averaging 23 years). Distal muscle weakness and atrophy of the lower extremities, especially anterior tibial muscle, was predominant in the early stage. Proximal and trunk muscles were involved in the advanced stage. Quadriceps femoris were slightly involved. The striking and characteristic pathological finding was the presence of rimmed vacuoles in atrophic muscle fibers with little evidence of necrotic or regenerative processes. Electron microscopy showed accumulation of myeloid structure and cytoplasmic or intranuclear tubofilamentous inclusion bodies. Although atrophy and weakness of the leg muscle appeared as initial symptoms, severe generalized skeletal muscle involvement with sparing of the facial, extraocular, bulbar, intercostals, and diaphragm muscles was recognized in the advanced stage. The patients became non-ambulant about 7-10 years after the onset of the disease. They lost the self-care ability and the quality of their life was rather low. The clinical and pathological features of the Chinese DMRV patients are basically similar to those of the Japanese patients. With the disease progressing slowly, the patients become wheelchair-bound and lose the self-care ability. As to daily life, the prognosis of DMRV is extremely poor.

A Gne knockout mouse expressing human GNE D176V mutation develops features similar to distal myopathy with rimmed vacuoles or hereditary inclusion body myopathy

Distal myopathy with rimmed vacuoles (DMRV) or hereditary inclusion body myopathy (hIBM) is an early adult-onset distal myopathy caused by mutations in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) gene which encodes for a bifunctional enzyme involved in sialic acid biosynthesis. It is pathologically characterized by the presence of rimmed vacuoles (RVs), especially in atrophic fibers, which also occasionally contain congophilic materials that are immunoreactive to beta-amyloid, lysosomal proteins, ubiquitin and tau proteins. To elucidate the pathomechanism of this myopathy and to explore treatment options, we generated a mouse model of DMRV/hIBM. We knocked out the Gne gene in mice but this resulted in embryonic lethality. We therefore generated a transgenic mouse that expressed the human GNE D176V mutation, which is one of the most prevalent mutations among Japanese DMRV patients, and crossed this with Gne(+/-) mice to obtain Gne(-/-)hGNED176V-Tg. Interestingly, these mice exhibit marked hyposialylation in serum, muscle and other organs. Reduction in motor performance in these mice can only be seen from 30 weeks of age. A compelling finding is the development of beta-amyloid deposition in myofibers by 32 weeks, which clearly precedes RV formation at 42 weeks. These results show that the Gne(-/-)hGNED176V-Tg mouse mimics the clinical, histopathological and biochemical features of DMRV/hIBM, making it useful for understanding the pathomechanism of this myopathy and for employing different strategies for therapy. Our findings underscore the notion that hyposialylation plays an important role in the pathomechanism of DMRV/hIBM.

A Gne knockout mouse expressing human V572L mutation develops features similar to distal myopathy with rimmed vacuoles or hereditary inclusion body myopathy

Distal myopathy with rimmed vacuoles (DMRV) or hereditary inclusion myopathy (h-IBM) is an early adult-onset distal myopathy caused by mutations in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) gene which encodes for a bifunctional enzyme involved in sialic acid biosynthesis. It is pathologically characterized by the presence of rimmed vacuoles especially in atrophic fibers, which also occasionally contain congophilic materials that are immunoreactive to beta-amyloid, lysosomal proteins, ubiquitin and tau proteins. To elucidate the pathomechanism of this myopathy and to explore the treatment options, we generated a mouse model of DMRV/h-IBM. We knocked out the Gne gene in the mouse, but this resulted in embryonic lethality. We therefore generated a transgenic mouse that expressed the human GNEV572L mutation, which is the most prevalent among Japanese DMRV patients, and crossed this with Gne((+/-)) mouse to obtain Gne((-/-))hGNEV572L-Tg. Interestingly, these mice exhibit marked hyposialylation in serum, muscle and other organs. Reduction in motor performance in these mice can only be seen from 30 weeks of age. A compelling finding is the development of beta-amyloid deposition in myofibers by 32 weeks, which clearly precedes rimmed vacuole formation at 42 weeks. These results show that the Gne((-/-)) hGNEV572L-Tg mouse mimics the clinical, histopathological and biochemical features of DMRV/h-IBM, making it useful for understanding the pathomechanism of this myopathy and for employing different strategies for therapy. Our findings underscore the notion that hyposialylation plays an important role in the pathomechanism of DMRV/h-IBM.

Heterozygous mutations affecting the epimerase domain of the GNE gene causing distal myopathy with rimmed vacuoles in a Taiwanese family

Objectives Studies of distal myopathy with rimmed vacuoles (DMRV) revealed that most patients had mutations in the UDP- N-acetylglucosamine 2-epimerase/ N-acetylmannosamine kinase (GNE) gene. However, the correlation between GNE mutations and clinical features was not fully understood. Purposes To report the correlation between the clinical features and genetic analysis of DMRV patients. Patients and methods The clinical presentations, histopathological findings, image studies, and genetic analyses of two patients with DMRV from a Taiwanese family were studied. Results Two compound heterozygous mutations, Ile 241 Ser and Arg 246 Gln, located in the epimerase domain, were identified in both patients, who were of the same generation. In addition, the elder sister showed a progressive muscular dystrophy course with severe quadriceps and trunk muscle involvement. Conclusion The compound heterozygous mutations in the epimerase domain of the GNE gene are important in the severe phenotype of DMRV. However, the mechanisms leading to this phenotypic heterogeneity still remain to be elucidated.

Distal Myopathy with Rimmed Vacuoles: Impaired O-Glycan Formation in Muscular Glycoproteins

Distal myopathy with rimmed vacuoles (DMRV), is an autosomal recessive disorder with early adult onset, displays distal dominant muscular involvement and is characterized by the presence of numerous rimmed vacuoles in the affected muscle fibers. The pathophysiology of DMRV has not been clarified yet, although the responsible gene was identified as that encoding UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase involved in the biosynthesis of sialic acids. To identify defective carbohydrate moieties of muscular glycoproteins from DMRV patients, frozen skeletal muscle sections from seven patients with DMRV, as well as normal and pathological controls, were treated with or without sialidase or N-glycosidase F followed by lectin staining and lectin blotting analysis. The sialic acid contents of the O-glycans in the skeletal muscle specimens from the DMRV patients were also measured. We found that Arachis hypogaea agglutinin (PNA) lectin reacted strongly with sarcolemmal glycoproteins in the DMRV patients but not with those in control subjects. alpha-Dystroglycan from the DMRV patients strongly associated with PNA lectin, although that from controls did not. The sialic acid level of the O-glycans in the DMRV muscular glycoproteins with molecular weights of 30 to 200 kd was reduced to 60 to 80% of the control level. The results show that impaired sialyl O-glycan formation in muscular glycoproteins, including alpha-dystroglycan, occurs in DMRV.

Distal myopathy with rimmed vacuoles is allelic to hereditary inclusion body myopathy.

Distal myopathy with rimmed vacuoles (DMRV) is an autosomal-recessive disorder with preferential involvement of the tibialis anterior muscle that starts in young adulthood and spares quadriceps muscles. The disease locus has been mapped to chromosome 9p1-q1, the same region as the hereditary inclusion body myopathy (HIBM) locus. HIBM was originally described as rimmed vacuole myopathy sparing the quadriceps; therefore, the two diseases have been suspected to be allelic. Recently, HIBM was shown to be associated with the mutations in the gene encoding the bifunctional enzyme, UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE). To determine whether DMRV and HIBM are allelic. The GNE gene was sequenced in 34 patients with DMRV. The epimerase activity in lymphocytes from eight DMRV patients was also measured. The authors identified 27 unrelated DMRV patients with homozygous or compound-heterozygous mutations in the GNE gene. DMRV patients had markedly decreased epimerase activity. DMRV is allelic to HIBM. Various mutations are associated with DMRV in Japan. The loss-of-function mutations in the GNE gene appear to cause DMRV/HIBM.