Myocarditis (slide #9)

This 54-year-old man had a 5 year history of amyotrophic lateral sclerosis (ALS). He had been in relatively good condition until the past year, during which he had developed multiple episodes of pneumonia and required nursing home care. He was receiving an experimental protocol agent for ALS at the time of his death. The heart grossly showed no abnormalities.

There is widespread microscopic infiltration of the myocardium by inflammatory cells, an intermixture of neutrophils and lymphocytes. The inflammation is seen within the interstitial connective tissue and also surrounding myocytes, which are undergoing degeneration (appearing fragmented and partly eroded). Note, that in distinction to acute myocardial infarction, the nuclei of myocytes are intact and coagulative necrosis has not occurred.

Checklist: Have you identified

myocyte breakdown
inflammation in the interstitium
neutrophils and lymphocytes specifically
inflammation around degenerating myocytes

Questions

1. What are the major causes of myocarditis?
2. How can the various causes be histologically differentiated?

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