Abstract | March 24, 2024

Heart of the Matter: Unmasking an Uncommon Culprit in Dilated Cardiomyopathy

Moyan Sun, DO, Internal Medicine Resident PGY2, Northeast Georgia Medical Center, Gainesville, GA

Vikas Kilaru, DO, Internal Medicine, PGY2, Northeast Georgia Medical Center, Gainesville, GA; Aleksandros Mihilli, MD, Internal Medicine, PGY3, Northeast Georgia Medical Center, Gainesville, GA; Giancarlo Acosta, MD, Department of Cardiology, Northeast Georgia Medical Center, Gainesville, GA

Learning Objectives

  1. Describe the clinical presentation of dilated cardiomyopathy and identify one uncommon etiology
  2. Recognize the diagnostic approach to new-onset heart failure and cardiomyopathy

Introduction: Dilated cardiomyopathy (DCM) has a myriad of causes but is often deemed idiopathic as no etiology can be readily identified. Herein, we present a rare case of DCM due to the 49-51 exon deletion of the Duchenne muscular dystrophy (DMD) gene, a rarely reported finding in the literature.

Case Presentation: A previously healthy 45-year-old female presented to the emergency department with 4 weeks of progressive dyspnea on exertion and orthopnea. Vitals signs are unremarkable, and physical examination showed bibasilar rales and 1+ bilateral leg edema. Labs revealed NT-proBNP of 6,305 pg/mL and trended troponins peaking at 36 ng/L. EKG showed normal sinus rhythm and persistent left-bundle branch block. A CT chest showed cardiomegaly with bibasilar ground glass opacities, but no focal infiltrates and a subsequent echocardiogram revealed a left ventricular (LV) ejection fraction (EF) of 20% with grade III LV diastolic dysfunction. She received three days of aggressive diuresis with mild clinical improvement and subsequently underwent coronary catheterization, which showed normal coronary arteries. At this point, her infectious work-up, including viral cultures, returned negative. A cardiac MRI showed LV EF of 12% but no evidence of prior infarction or myocarditis. Genetic testing ultimately revealed the deletion of exon 49-51 of the DMD gene.

Final Diagnosis: Dilated cardiomyopathy due to DMD

Management and Outcome: She received continued diuresis, and she was initiated guideline-direct medical therapy. She had complete symptom resolution at outpatient follow-up and is considering genetic counseling for her family. Isolated DCM caused by DMD is rare. DCM is characterized by the dilatation and systolic dysfunction of one or more ventricles, and it is estimated that 30-45% of cases of idiopathic DCM can be attributed to familial DCM. DMD is caused by variable expression of dystrophin, which plays a vital role in muscle cytoskeleton cross-linking and integrity. Several pathogenic gene mutations have been identified, but the exon 49-51 deletion of the DMD gene has only been reported twice; previously, it was also associated with isolated DCM in female patients. Thus, it is essential to consider DMD as an etiology of DCM, especially in female patients without cardiovascular risk factors.

References and Resources

  1. Ulm EA, Nagaraj CB, Tian C, Smolarek TA. Identification of Biallelic dystrophin gene variants during maternal carrier testing for Becker muscular dystrophy and review of the DMD exon 49-51 deletion phenotype. Mol Genet Genomic Med. 2023 Jan;11(1):e2088. doi: 10.1002/mgg3.2088. Epub 2022 Nov 24. PMID: 36424846; PMCID: PMC9834199.
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