BACKGROUND: Bethlem myopathy is a congenital myopathy presenting with muscle weakness and joint abnormalities. Although cardiac involvement is frequent in other inherited myopathies, it has not yet been described in Bethlem myopathy.
CASE: We report a case of progressive deterioration of left ventricular function during pregnancy in a patient with Bethlem myopathy. Worsening of clinical symptoms, particularly dyspnea, necessitated delivery at 36 2/7 weeks of gestation. Myocardial function recovered postpartum with improvement of clinical symptoms.
CONCLUSION: Bethlem myopathy may be associated with progressive left ventricular dysfunction during pregnancy and may require early delivery.