Cardiac Path Online
Pathology of Giant Cell Myocarditis
Idiopathic Giant Cell
Giant cell myocarditis is a rare inflammatory disease of the myocardium that often affects previously healthy young adults.
Related post: Myocarditis.
It is usually fatal without treatment, and may respond to aggressive medical and surgical therapy.
Giant cell myocarditis is most often progressive over days to weeks and frequently requires the concurrent management of congestive heart failure, tachyarrhythmias, and heart block.
Gross: Gross appearance of the heart is not unlike that seen in myocarditis associated with known infectious agents, the essential features being dilatation and sometimes hypertrophy.
When the lesions are extensive, they appear as yellow-gray or gray foci throughout the myocardium.
Mural thrombi are commonly present.
Granulomatous inflammation of the heart:
Rheumatic Fever - A specific lesion characterized by granulomas known as Aschoff's nodules (they contain Aschoff's cells which are uni- or multinucleated histiocytes with a serrated nuclear chromatin bar).
Rheumatic myocarditis is characterized by the presence of interstitial Aschoff's nodules adjacent to small intramyocardial arteries, and an absence of widespread necrosis.
Well-developed granulomas occur in sarcoidosis -
(i) Absence of well formed granulomas in Giant cell myocarditis.
(ii) The lack of involvement of the epicardial fat in Giant cell myocarditis. In cardiac sarcoidosis, granulomas are seen in the epicardial fat.
(iii) Prominent eosinophilia in the inflammatory cellular infiltrate present in Giant cell myocarditis. It is usually absent in cardiac sarcoidosis.
Infectious granulomatous myocarditis : Granulomas are noted in lesions caused by infective agents (tuberculosis, fungal and parasitic disorders). Necrotizing granulomas in infectious conditions should be excluded with histochemical stains and cultures. Acid-fast bacilli and spirochetes cannot be demonstrated.
Idiopathic lymphocytic myocarditis : Giant cells are usually not prominent. Absence of widespread necrosis.
In metabolic disorders- Granulomas occur in gout (in which tophi are associated with calcific deposits and with a foreign body cellular reaction), the various syndromes of oxalosis (in which oxalate deposits also lead to a foreign body reaction), and in chronic granulomatous disease of childhood.
Reaction to foreign bodies: Granulomas occur as a reaction to foreign bodies and devices implanted within the cardiovascular system. Foreign body granuloma
Related post: Granulomatous Reaction Pattern of the Skin
Treatment includes immunosuppressives, and the indication for cardiac transplantation should be evaluated early, as there is an increased risk of recurrence in the graft.
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