title: Atrial giant cell myocarditis: a distinctive clinicopathologic entity.
abstract: BACKGROUND
  Giant cell myocarditis (GCM) typically causes fulminant heart failure, arrhythmias, or heart block, necessitating aggressive immunosuppression, ventricular assist device insertion, or cardiac transplantation. We describe a novel variant of GCM, primarily involving the atria, that displays distinctive clinical features and follows a more benign course than ventricular GCM.
  
  
  RESULTS
  We identified 6 patients (median age 67.5 years, 4 male) with atrial GCM in our pathology consultation practices from 2010 to 2012. Clinical history, imaging, and pathology materials were reviewed. Clinically, 4 patients had atrial fibrillation, 1 had acute heart failure, and 1 had incidental disease at autopsy. Among the 5 living patients, echocardiography revealed severe atrial dilatation (5 cases), mitral/tricuspid regurgitation (5), atrial mural thrombus (3), atrial wall thickening (2), and atrial hypokinesis (2). Ventricular function was preserved in all 5. Histological review of surgically resected atria showed giant cell and lymphocytic infiltrates, lymphocytic myocarditis-like foci, cardiomyocyte necrosis, and cardiomyocyte hypertrophy in all cases. Other features included interstitial fibrosis (5), poorly-formed granulomas (4), eosinophils (4), neutrophils (1), and vasculitis (1). Treatment consisted of steroids and cyclosporine (1), pacemaker placement for sick sinus syndrome (1), and supportive care (3). All 5 living patients returned to baseline exercise tolerance after 6 to 16 weeks of follow-up.
  
  
  CONCLUSIONS
  Atrial GCM represents a distinct clinicopathologic entity with a more favorable prognosis than classic ventricular GCM. This disorder should be included in the differential diagnosis of atrial dilatation, particularly when associated with atrial wall thickening. The utility of immunomodulatory therapy for this condition remains unknown.
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Brandon T
authors.initials: BT
authors.lastname: Larsen
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Maleszewski
authors.forename: William D
authors.initials: WD
authors.lastname: Edwards
authors.forename: Leslie T
authors.initials: LT
authors.lastname: Cooper
authors.forename: Richard E
authors.initials: RE
authors.lastname: Sobonya
authors.forename: V Eric
authors.initials: VE
authors.lastname: Thompson
authors.forename: Simon G
authors.initials: SG
authors.lastname: Duckett
authors.forename: Charles R
authors.initials: CR
authors.lastname: Peebles
authors.forename: Iain A
authors.initials: IA
authors.lastname: Simpson
authors.forename: Henry D
authors.initials: HD
authors.lastname: Tazelaar
mesh_terms: D000328:Adult; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000209:etiology / Q000473:pathology*; D018450:Disease Progression; D005260:Female; D005355:Fibrosis; D015726:Giant Cells / Q000473:pathology*; D006325:Heart Atria / Q000473:pathology; D006333:Heart Failure / Q000209:etiology / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009205:Myocarditis / Q000145:classification* / Q000150:complications / Q000473:pathology*; D009206:Myocardium / Q000473:pathology*; D032383:Myocytes, Cardiac / Q000473:pathology; D009336:Necrosis; D011379:Prognosis