Bethlem myopathy
Dominantly inherited mild diease associating congenital muscle weakness, proximal joint contractures and marked distal joint hyperextensibility. Bethlem myopathy shows clear dominant inheritance and is caused by heterozygous mutations in COL6A1, COL6A2 and COL6A3.
Etiology
heterozygous mutations in COL6s collagen genes (COL6A1, COL6A2 and COL6A3)