Abstract 2009: More than Just “a Lazy Boy”
We present a case of new onset heart failure of rare etiology, with diagnostic clues embedded in history and physical exam. S.R. is a 22 yo male who presented to a local ER with two days of progressive dyspnea on exertion, orthopnea, and dry cough. He described having low grade fevers, generalized fatigue, weakness, and anorexia over the preceding 2 weeks. He was found to be in cardiogenic shock, with echocardiography showing a severely dilated left ventricle, no effusion, and EF <10%. He was started on dopamine and dobutamine and transferred to our hospital, where cardiac catheterization revealed elevated filling pressures (PCWP 27mmHg) and a cardiac index of 2.18 L/min/m2. He was intubated for hypoxia, and an intra-aortic balloon pump was placed. SR has no significant past medical history and does not use tobacco, alcohol or illicit drugs. He has no family history of cardiac or genetic disorders. His mother describes SR as “a good kid, but a lazy boy,” not interested in physical activities. This information helped to direct our work-up. Initial labs revealed a total CPK of 5494 U/L, with MB fraction only 47 ng/mL, and TropI 2.77 ng/mL. Over the next several days, further lab tests revealed a normal drug screen, thyroid panel, HIV, ESR, and ANA. Viral serologies were negative. CPK remained >5000 U/L for 3 days then plateaued. On hospital day 2, SR was extubated and weaned off the IABP. However, he remained extremely weak with nearly flaccid muscle tone. EMG showed a myopathic process. Cardiac muscle biopsy revealed myocyte hypertrophy and fibrosis, particularly in the left ventricular wall. Skeletal muscle biopsy showed a mild dystrophic process. H&E stains revealed mild inflammation and fibrosis. Dystrophin staining showed a clear mosaicism with a majority of positive fibers for dystrophin and alpha-sarcoglycan in a pattern suggestive of a carrier of Duchenne Muscular Dystrophy (DMD). DMD is an X-linked recessive disease causing complete absence of dystrophin. Cardiac manifestations include ECG changes, dilated cardiomyopathy, and conduction defects. DNA sampling for DMD was negative for our patient, but sensitivity is reportedly 50% in cases of somatic mosaicism. SR was diagnosed with a somatic mosaic variant of DMD with associated dilated cardiomyopathy.