1 2 aim

#apaperaday: Diverse Cardiac Phenotype of Becker Muscular Dystrophy: Under-Recognized Subclinical Cardiomyopathy Due to Partial Dystrophin Deficiency in a Contemporary Era

In today’s #apaperaday, Prof. Aartsma-Rus reads and comments on the paper titled:  Diverse Cardiac Phenotype of Becker Muscular Dystrophy: Under-Recognized Subclinical Cardiomyopathy Due to Partial Dystrophin Deficiency in a Contemporary Era

Becker themed for the back from the @Parent_Project  meeting. Today’s pick is from Migam et al from Pediatric cardiology and is a long term follow up of heart pathology in a cohort of Becker patients. DOI 10.1007/s00246-023-03382-9

Becker is a progressive muscle disease that can also be associated with heart pathology. Like the muscle pathology, heart symptoms vary between patients, from heart failure, severe dilated cardiomyopathy, sudden death to no pathology.

Authors here describe a cohort of 25 Becker patients who were diagnosed between 2008 and 2019 in Delaware (USA). A confirmation of a dystrophin mutation was available for all patients. There was an average of 9.5 year follow up data available.

For 3 patients there was acute progression during follow up, 6 had chronic persistent pathology and 16 had latent pathology. The patients with pathology had left ventricular dysfunction, 3 with heart failure, 1 of whom died.

All patients had increased levels of CK and transaminases (from muscle not from liver!) There was no correlation between CK or transaminase levels or muscle symptom severity and heart pathology.

1 patient had severe progression of muscle weakness and needed a wheelchair by age 10. However, he had many comorbidities including a cerebral infarct which probably played a role.

ECGs were done for 23 patients showing normal ECGs for 10 patients and abnormalities in 13, including a conduction delay in 1 patient. No influence of the genotype (location of mutation) was found with the severity or presence of heart problems.

Authors discuss 36% of their cohort progressed during follow up, while they were normal at time of diagnosis. They also stress that like in Duchenne, Becker patients have higher levels of transaminases in their blood due to muscle pathology. This is not a sign of liver pathology.

The right ventricle was normal in this cohort. No correlations with genotype & heart pathology were found, while other studies did find this. Authors argue individual cohorts are generally small which makes finding robust correlations difficult with the variability in Becker

Authors also outline that while in Duchenne patients often have atrophic hearts, Becker patients have hypertrophic hearts. They stress that diagnosing heart pathology is important as it allows management with e.g. ace inhibitors and beta blockers.

They also mention that guidelines are needed for what safe exercise would be for Becker patients. The limitations of the study are the small cohort and the retrospective nature. No MRI was done, which is more sensitive than ECG.

A limitation the authors do not mention is that there are multiple family members in their cohort. They stress the importance of identifying heart problems and that pathology can be subclinical and t in Becker may present different than in Duchenne rather than being ‘milder’

I think the latter is an important message. The concept that Becker is a mild disease is of course only from the perspective of Duchenne and reflects skeletal muscle pathology. However, the heart pathology is different, and may be more risky as patients are more active.