Journal of the Louisiana State Medical Society
Inclusion Body Myositis Masquerading as Cardiac Dyspnea
Siu-Hin Wan, MD; Jackson J. Liang, DO; Andrew C. Greenlund, MD, PhD
Dyspnea in the elderly can be due to a wide array of pathologies. We discuss a case of an elderly gentleman with an extensive cardiovascular history presenting with acute worsening of chronic dyspnea. Because of persistent respiratory distress unresponsive to standard therapy for congestive heart failure, chronotropic insufficiency, and pulmonary hypertension, further evaluation was undertaken which revealed that dia- phragmatic weakness was the etiology of his respiratory failure. EMG and muscle biopsy confirmed the diagnosis of inclusion body myositis (IBM).
INTRODUCTION While respiratory failure is a frequent complication from advanced and longstanding IBM, it is unusual for dyspnea to be a presenting symptom of the disease. The literature on IBM has commonly focused on neurological symptoms, such as proximal weakness, as the cardinal presenting features of IBM. We present a case of dyspnea due to IBM initially thought to be cardiogenic in nature. Our case demonstrates the importance of performing a complete history and physical examination in evaluation of dyspnea, and, to maintain a broad differential diagnosis, considering other less common causes whenmore frequent cardiovascu- lar and pulmonary etiologies have been excluded. CASE PRESENTATION An 81-year-old gentleman was seen by his primary care provider over four months in early 2012 at Mayo Clinic in Rochester, Minnesota for persistent dyspnea on exertion. His past medical history was notable for coronary artery disease, status post-coronary artery bypass grafting with multiple percutaneous interventions, a permanent pace- maker, congestive heart failure, restrictive lung disease, and obstructive sleep apnea. The dyspnea he complained of was distinct from his previous episodes of angina, with his last percutaneous coronary intervention with a drug eluting stent having occurred approximately one year prior to presentation. Echocardiography demonstrated an ejection fraction of 55% with a right ventricular systolic pressure of 55 mmHg. Decreased inspiratory collapse of his inferior vena cava was noted. Trials of aggressive diuretic therapy failed to improve his dyspnea. Pulmonary embolismwas ruled out with chest computed tomograpy angiography. Right-sided heart cath-
eterization was performed, which confirmed the presence of pulmonary hypertension. A trial of phosphodiesterase inhibitor therapy failed to improve his symptoms. Pulmo- nary function tests demonstrated little change from previ- ous studies, with a vital capacity of 1.32 L (37% predicted), FEV1 0.88 L (32% predicted), FEV1/FVC 73.7%, and DLCO 8.0 mL CO/min/mmHg (36% predicted). His permanent pacemaker, which had been placed 15 years prior for carotid hypersensitivity and intermittent pacemaker dependency, was interrogated and found to be functioning appropriately. Subsequent to the development of his dyspnea, a left foot dropwas noted. He was evaluated by a physiatrist who believed the etiology to be either a peroneal neuropathy or S-1 radiculopathy. The patient believed the foot drop was improving and an electromyogram was deferred. General- ized gait impairment was attributed to deconditioning from decreasedmobility due to exercise intolerance and exertional dyspnea, and a walker was prescribed. This patient then presented to the emergency depart- ment with acute progression of dyspnea that was signifi- cantly impacting completion of his daily activities. While the patient had a good cough reflex, he had a paradoxical breathing pattern and substantial accessory muscle use, concerning for diaphragmatic dysfunction. Strength test- ing demonstrated neck flexor weakness, as well as bilateral deltoid and iliopsoas weakness. Distal muscle strength was preserved. Toeswere downgoing on Babinski’s examination. Laboratory investigation was significant for anemia (hemoglobin 10.7 g/dL, normal 13.5-17.5) and a creatinine of 1.5 mg/dL (normal 0.8-1.3). Initial troponin T was 0.24 ng/ mL (normal <0.01) and remained unchanged after three and six hours. NT-pro-BNPwas 1,900 pg/mL (normal <131), and arterial blood gas showed a pH of 7.35, PCO2 of 54 mmHg, and PO2 of 85 mmHg. Creatine kinase was normal, and aldolase was found to be 9.5 U/L (normal <7.7).
254 J La State Med Soc VOL 166 November/December 2014
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