Prevalence of Elevated Serum IgG4 Level among Patients Diagnosed or Suspected with Cardiovascular Disorders.

Immunoglobulin G4 (IgG4)-related disease, that is characterized by the elevation of circulating IgG4 level and the tissue-infiltration of IgG4-positive plasma cells, can target the cardiovascular tissue, although the diagnosis of IgG4-related cardiovascular lesion is not easy owing to the substantial risk for the tissue sampling. We herein examined the serum IgG4 levels among cardiac patients. In patients who were admitted to the cardiology department (n=477) and those who underwent computed tomography coronary artery angiography (n=401), elevated serum IgG4 level (≥135 mg/dL) was found 23 (4.8%) and 17 (4.2%), respectively. However, among those with elevated serum IgG4, only two patients could be clinicopathologically diagnosed with IgG4-related disease. Cardiovascular organ involvement may aggravate the prognosis of IgG4-related disease which in general not life-threatening. Considering that the non-negligible prevalence of high IgG4 level among cardiac patients who were not diagnosed with IgG4-related disease, however, physicians should not count too much on the serum IgG4 levels for the diagnosis of IgG4-related cardiovascular lesions, especially when histopathologic findings are not available, or when other-tissue involvement of IgG4-related disease is not apparent. (This is a translation of J Jpn Coll Angiol 2017; 57: 91-98.).