Muscular Dystrophy With Associated HCM
Becker Muscular Dystrophy (BMD) and Duchenne Muscular Dystrophy (DMD) are two types of muscular dystrophy that have cardiac involvement (CI), sometimes in the form of hypertrophic cardiomyopathy (HCM). DMD is one of nine types of Muscular Dystrophy (MD) and is a genetic disorder caused by the absence of the protein, dystrophin. The inheritance pattern of DMD is categorised as an X-linked recessive disorder. Much like DMD, BMD is also an X-linked recessive disorder that manifests as a lack of dystrophin. The difference between the two is that the voluntary muscles have better function, the progression is slower and less predictable. Due to the genetic nature of BMD and DMD, there are both exhibitors and carriers of the disease. Carriers can also present with CI but at a very decreased level in comparison to exhibitors.
MD patients experience a series of symptoms such as progressive muscle weakening, loss of muscle mass, and CI. In BMD patients have more control over their involuntary functions and the disease progresses at a slower rate than DMD. CI however presents similarly in both. In BMD, CI is rarely completely absent and patients will most likely experience some sort of CI at some point in their life, however they will not necessarily manifest as HCM. There is no correlation between the severity of CI and the level of skeletal muscle manifestations. Usually HCM evolves into DCM in BMD patients. In rare cases, the progression from HCM to DCM occurs rapidly and can potentially be life threatening. Patients will be affected by any number of the symptoms normally associated with HCM or may be asymptomatic.
BMD occurs at one tenth the rate of DMD. In both DMD and BMD, Dilated Cardiomyopathy (DCM) is more frequent than HCM. DMD and BMD are estimated to affect about 1 in 7,250 males. DMD present in male 3-5 years old where as BMD usually does not manifest until the late teens to early twenties. Prognosis for DMD patients is generally into the early 30’s, where as the prognosis for BMD is into the 40’s.
For any non cardiac symptoms of MD patients should see a neurologists specialize in treating MS. As soon as possible post diagnosis of CI, patients should see a cardiologist or a Hypertrophic Cardiomyopathy Association (HCMA) recognized Center of Excellence (COE) if diagnosed with HCM. The HCMA is happy to assist with cardiac related issues, however the Muscular Dystrophy Association (MDA) has greater resources for multidisciplinary care.
Figure 1. Bright Blood Cardiac MRI of a patient with DMD and HCM
Josef Finsterer, MD PhD1, Claudia Stöllberger, MD Canadian Journal of Cardiology.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2643160/ . Accessed April 12th, 2018.
“Muscular Dystrophy” Center for Diseas Control and Prevention https://www.cdc.gov/ncbddd/musculardystrophy/data.html Acessed April 19th, 2018
“ Duchenne Muscular Dystrophy (DMD)” Muscular Dystrophy Association https://www.mda.org/disease/duchenne-muscular-dystrophy Acessed April 19th, 2018
“Becker Muscular Dystrophy (BMD)” Muscular Dystrophy Association
https://www.mda.org/disease/becker-muscular-dystrophy Acessed April 19th, 2018
“Becker Muscular Dystrophy” National Institute of Health
https://rarediseases.info.nih.gov/diseases/5900/becker-muscular-dystrophy Acessed April 19th, 2018