We report three cases of Bethlem myopathy from three consecutive generations of a Taiwanese family, including one woman aged 70, one man aged 40, and a boy aged 8. The clinical features of the patients included autosomal dominant inheritance, childhood or adolescent onset, mainly proximal and extensor involvement, early diffuse joint contractures, and absence of cardiac involvement. These features fulfilled the diagnostic criteria for Bethlem myopathy. Though the clinical course of the disease was once thought to be benign, our female patient became wheelchair-bound at the age of 53. This suggests that the disease process in Bethlem myopathy is slow but ongoing.