Mexico's First Heart Transplant in a Patient with Becker Muscular Dystrophy Reveals an Overlooked Cause of Idiopathic Dilated Cardiomyopathy.

BACKGROUND: Pathogenic variants in the DMD gene are a frequently overlooked cause of dilated cardiomyopathy (DCM) in idiopathic cases, especially when skeletal myopathy is mild or seemingly absent. Becker muscular dystrophy (BMD) and X-linked dilated cardiomyopathy are at opposite ends of this clinical spectrum but result from pathogenic variants in the same gene. Cardiomyopathy is a major cause of premature death in muscular dystrophies. CASE PRESENTATION: We describe a 37-year-old man who underwent orthotopic heart transplantation for presumed idiopathic DCM with refractory heart failure. He had a six-year history of progressive proximal weakness, pseudohypertrophy of the calf, a positive Gowers sign, and markedly elevated creatine kinase (6638 IU/L). Multiplex ligation-dependent probe amplification (MLPA) revealed an in-frame deletion of exons 45-47 of DMD [c. (6438+1_6439-1)_(6912+1_6913-1) del; NM_004006.2], confirming BMD. Immunofluorescence showed reduced and patchy dystrophin expression. CONCLUSIONS: To our knowledge, this is the first documented heart transplant in a patient with BMD in Mexico. This case demonstrates the value of considering muscular dystrophy in the differential diagnosis of apparently idiopathic dilated cardiomyopathy (DCM), a step that opens the door to accurate diagnosis, carrier screening, and genetic counseling, and supports the view that heart transplantation is a viable option in carefully selected patients with muscular dystrophy cardiomyopathy.