Bobo–Newton acute myocarditis caused by Capnocytophaga canimorsus: a case report

Capnocytophaga canimorsus is a Gram-negative bacillus commensal of the oral cavities of dogs and cats that can cause human infection after a bite or scratch. Cardiovascular manifestations have included endocarditis, heart failure, acute myocardial infarction, mycotic aortic aneurysm and prosthetic aortitis.

A 37-year-old male presented septic manifestations, ST-segment alterations on the electrocardiogram and troponin rise, 3 days after a dog bite. N-terminal brain natriuretic peptide was elevated and transthoracic echocardiography revealed mild diffuse left ventricular (LV) hypokinesia. Coronary computed tomography angiography showed normal coronary arteries. Two aerobic blood cultures grew Capnocytophaga canimorsus. On Day 5, cardiovascular magnetic resonance (CMR), showed all diagnostic criteria of acute myocarditis, including focal areas of subepicardial oedema in the LV inferolateral wall, early hyperenhancement, nodular or linear foci of late gadolinium enhancement, increased T2-times and extracellular volume fraction. The outcome was favourable with amoxicillin.

Four cases of myocardial infarction caused by Capnocytophaga canimorsus had been reported and coronary angiography showed normal coronary arteries in 3 cases. Herein, we report a case of documented acute myocarditis associated with Capnocytophaga canimorsus infection. Myocarditis was demonstrated by comprehensive CMR revealing all established diagnostic criteria. Acute myocarditis should be ruled out in patients with Capnocytophaga canimorsus infection and a clinical presentation of “acute myocardial infarction”, especially in those with unobstructed coronary arteries.