Cause of Cardiac Disease in a Female Carrier of Duchenne Muscular Dystrophy
Myocarditis Versus Genetic Cardiomyopathy Without Skeletal Myopathy?
A 51-year–old woman experienced a respiratory tract infection with fever followed by persistent fatigue and muscle pain in her extremities for >2 months. Family history revealed a 30-year–old wheelchair-bound son with advanced myopathy suffering from Duchenne muscular dystrophy (DMD; deletion in the dystrophin gene). Blood analysis in the mother revealed an elevated total creatine kinase (CK) level of 479 U/L (normal, <190 U/L) with a normal creatine kinase-MB (CK-MB) level of 17 U/L (normal, <25 U/l). Additional workup of (skeletal) myopathy was composed of a calf muscle biopsy with normal histopathologic findings (Figure 1): in particular, there were no signs of structural abnormalities, inflammation, or dystrophin deficiency. Genetic analysis of blood cells revealed a heterozygous dystrophin gene mutation, and the female patient was identified as a–probably symptomatic–DMD carrier.
In addition to muscle pain, she was also experiencing dyspnea on exertion and fatigue and, therefore, presented to our hospital. She was in an acceptable general condition, and her physical examination was unremarkable. Her resting ECG demonstrated sinus rhythm without any repolarization abnormalities. A cardiovascular magnetic resonance imaging (CMR) study was performed on a …