Differential Diagnosis for Possible Myocarditis

• Single most likely diagnosis
  • Viral myocarditis: This is the most common cause of myocarditis, often resulting from viral infections such as coxsackievirus B, which directly damages the heart muscle.
• Other Likely diagnoses
  • Bacterial myocarditis: Caused by bacterial infections, this form of myocarditis can occur in the setting of endocarditis or direct bacterial invasion of the heart muscle.
  • Autoimmune myocarditis: Conditions like systemic lupus erythematosus (SLE) or rheumatoid arthritis can lead to autoimmune myocarditis, where the body's immune system attacks the heart muscle.
  • Toxic myocarditis: Exposure to certain drugs (e.g., chemotherapy agents) or toxins can cause myocarditis.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Acute coronary syndrome: Although myocarditis and acute coronary syndrome have different pathophysiologies, their presentations can overlap, making it crucial to rule out coronary artery disease, especially in older adults or those with risk factors for coronary artery disease.
  • Giant cell myocarditis: A rare but aggressive form of myocarditis with a high mortality rate if not promptly treated, often requiring immunosuppressive therapy.
  • Sarcoidosis: Cardiac involvement in sarcoidosis can mimic myocarditis and requires specific treatment to prevent serious complications.
• Rare diagnoses
  • Eosinophilic myocarditis: Associated with conditions like Loeffler's endocarditis or hypersensitivity reactions, this form of myocarditis is characterized by eosinophilic infiltration of the heart muscle.
  • Chagas disease: Caused by Trypanosoma cruzi, this parasitic infection can lead to myocarditis, particularly in individuals from or traveling to endemic areas of Central and South America.
  • Lyme carditis: A manifestation of Lyme disease, caused by Borrelia burgdorferi, which can lead to myocarditis among other cardiac complications.