Eosinophilic myocarditis is a rare myocardial inflammation that is probably underrecognized and underdiagnosed. The underlying causes of eosinophilic infiltration of the myocardium include hypersensitivity reactions, immune-mediated disorders (such as eosinophilic granulomatosis with polyangiitis), hypereosinophilic syndrome, infections, and cancer. The prevalence of these disorders as causes of myocarditis is unclear; however, studies have reported that hypersensitivity reactions are the most common. Drugs that have been implicated as offending agents include antibiotics, sulfonamides, anticonvulsants, anti-inflammatory medications, and diuretics. Interestingly, dobutamine infusion has been observed to cause eosinophilic myocarditis. It is unclear whether this is due to hypersensitivity to the medication or to its preservative, sodium bisulfite. Many cases of eosinophilic myocarditis have no identifiable cause.
The presentation of eosinophilic myocarditis can range from mild disease to fulminant cardiogenic shock associated with myocardial necrosis, as well as cardiac arrhythmias and sudden cardiac death. Necrotizing eosinophilic myocarditis has a poor prognosis, and the diagnosis is typically made during an autopsy. The disease can progress along three stages:
Stage 1 involves acute inflammation and subsequent myocardial necrosis.
Stage 2 involves endomyocardial thrombus formation.
Stage 3 involves myocardial fibrosis.
The third stage is known as chronic restrictive cardiomyopathy, or Loeffler cardiomyopathy or Loeffler endomyocarditis. In 1963, Dr Wilhelm Loeffler of Switzerland described this eponymous endomyocarditis as a diffuse eosinophilic infiltration of the myocardium associated with peripheral eosinophilia. Eosinophilic infiltration results in the secretion of protein granules that cause myocardial damage by direct production of toxins, which activate platelets. These activated platelets can form intracavitary thrombi and produce further myocardial injury.
Eosinophilic infiltration affects the cardiac electrical conduction system in addition to causing heart failure. Myocardial involvement can vary; it can appear in a focal location, in a patchy distribution, or as a diffuse infiltration. The degree of infiltration does not necessarily correlate with clinical symptoms. Signs and symptoms associated with eosinophilic myocarditis can be nonspecific and include fever, skin changes, tachycardia, and ST-segment or T-wave abnormalities. Eosinophilic myocarditis can also present as acute heart failure. Peripheral eosinophilia may not be present initially. One study demonstrated an increase in peripheral eosinophilia over 2-6 days after presentation. Therefore, serial monitoring of blood counts with differential is essential.
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Cite this: Priyanka Ghosh, Saurabh Sharma. Cardio Case Challenge: A Confused 35-Year-Old With Headache, Fever, and Sore Chest - Medscape - Jun 01, 2022.