[P3-131] Clinical and genetic perspectives of pediatric collagen VI-related myopathy patients
Collagen VI-related myopathy is known to have variable clinical spectrum, which causative genes are COL6A1, COL6A2, and COL6A3. This study was aimed to describe clinical characteristics and identify genetic spectrum of collagen VI-related myopathy patients. From July 2000 to July 2016, we enrolled 23 patients with genetically confirmed collagen VI-related myopathy. Medical record was reviewed retrospectively. The mean age of symptom onset was 19 months and mean follow-up duration was 7.7 years. Ten patients (43%) had congenital orthopedic problems. Three patients (13%) never walked and 7 (35%) lost their walking ability at the mean age of 10. Hyperlaxity of distal joints, contracture of proximal joints, and scoliosis were noted in 11 (48%) patients each. Six patients (26%) used mechanical ventilator. Clinically, patients were categorized as Ullrich type in 11 (48%), Bethlem type in 4 (17%), limb-girdle type in 3 (13%), and undetermined in 5 (22%). All patients showed sarcolemma-specific collagen VI deficiency in pathology. Mutations for COL6A1, COL6A2, and COL6A3 were found in 15 (65%), 3 (13%), and 5 (22%) patients. All variants were heterozygous and most of them located in the triple helical domain. Five novel variants were detected. Five patients with same variants, c.850G>A in COL6A1, revealed diverse clinical course, from unable to walk by 4 years old to step up independently over 20 years old. Two patients with arthrogryposis multiplex congenita never achieved walking ability. Conclusively, we verified heterogeneity in clinical features of collagen VI-related myopathy without genotype-phenotype association. Multiple congenital orthopedic problems might suggest poor prognosis.