PURPOSE: Glucosamine (UDP-N-acetyl)-2-epimerase/N-acetylmannosamine kinase (GNE) myopathy is an autosomal recessive neuromuscular disorder characterized by early adult-onset weakness of the distal muscles of the lower limbs. The clinical spectrum of GNE myopathy varies, and it is not clear how the same GNE gene mutations can result in different phenotypes. Here, we present clinical, pathological and genetic characteristics of twenty-one Korean patients with GNE myopathy. MATERIALS AND METHODS: Twenty-one GNE myopathy patients were included in this study, conducted from 2004 to 2011. Based on medical records, patients' gender, onset age, family history, clinical history, serum creatine kinase (CK) level, neurologic examination, findings of muscle biopsy, muscle imaging findings and electrophysiologic features were extensively reviewed. Mutation of the GNE gene (9p13.3) was confirmed by DNA direct sequencing analysis in all patients. RESULTS: The mean onset age was 23.8+/-8.8 years (mean+/-SD). Patient serum CK levels were slightly to moderately elevated, ranging from 41 to 2610 IU. Among the patients, twelve patients were female and nine patients were male. Except for eight patients, all of the patients presented initially with only distal muscle weakness in the lower extremities. The most common mutation was V572L, followed by C13S. CONCLUSION: The clinical manifestations of our patients with GNE mutations varied. Among twenty-one patients, thirteen patients showed the typical GNE myopathy phenotype. There was no relationship between clinical features and site of mutation. Therefore, we suggest that neither homozygous nor compound heterozygous models are correlated with disease phenotype or disease severity.
Adolescent ; Adult ; Creatine Kinase/blood ; Distal Myopathies/diagnosis/*genetics/pathology ; Female ; Humans ; Male ; Multienzyme Complexes/*genetics ; Republic of Korea ; Sequence Analysis, DNA

Dysferlinopathy is caused by mutations in the DYSF gene. To characterize the clinical spectrum, we investigated the characteristics of 31 Korean dysferlinopathy patients confirmed by immunohistochemistry. The mean age of symptom onset was 22.23 +/- 7.34 yr. The serum creatine kinase (CK) was highly increased (4- to 101-fold above normal). The pathological findings of muscle specimens showed nonspecific dystrophic features and frequent inflammatory cell infiltration. Muscle imaging studies showed fatty atrophic changes dominantly in the posterolateral muscles of the lower limb. The patients with dysferlinopathy were classified by initial muscle weakness: fifteen patients with Miyoshi myopathy phenotype (MM), thirteen patients with limb girdle muscular dystrophy 2B phenotype (LGMD2B), two patients with proximodistal phenotype, and one asymptomatic patient. There were no differences between LGMD2B and MM groups in terms of onset age, serum CK levels and pathological findings. Dysferlinopathy patients usually have young adult onset and high serum CK levels. However, heterogeneity of clinical presentations and pathologic findings upon routine staining makes it difficult to diagnose dysferlinopathy. These limitations make immunohistochemistry currently the most important method for the diagnosis of dysferlinopathy.
Adolescent ; Adult ; Age of Onset ; Creatine Kinase/blood ; Distal Myopathies/pathology ; Female ; Humans ; Immunohistochemistry ; Male ; Membrane Proteins/genetics ; Middle Aged ; Muscle Proteins/genetics ; Muscular Atrophy/pathology ; Muscular Dystrophies, Limb-Girdle/*diagnosis/genetics/pathology ; Mutation ; Phenotype ; Republic of Korea ; Tomography, X-Ray Computed ; Young Adult