Clinical Importance of IgG4-related Coronary Periarteritis.

To the Editor In a recent case report, Komiya et al. reported a 59-year-old man who had been diagnosed with immunoglobulin G4 (IgG4)-related disease involving the abdominal aorta, coronary artery, and presumably submandibular gland (1). In this patient, masses surrounding the coronary arteries were observed by pre-operative echocardiographic screening, and the size of these perivascular masses increased during the two-year follow-up. Corticosteroid therapy was started after surgical treatment for the abdominal aortic aneurysm (AAA), and it reduced the size of the masses surrounding the coronary arteries.

Considering that IgG4-related inflammatory AAA has been reported to comprise 40% of inflammatory AAAs and 5% of total AAAs (2), it is likely that IgG4-related coronary periarteritis has been overlooked or underdiagnosed in many patients with AAA. Recent studies have suggested that corticosteroid treatment might facilitate luminal dilation of the aneurysm (3), or, conversely, ameliorate the perivascular thickening and luminal narrowing in patients with IgG4-related coronary periarteritis (4). Several previous studies have demonstrated the unfavorable outcome of IgG4-related coronary periarteritis (5), but the possibility of publication bias should also be taken into account.

However, without myocardial ischemia or aneurysm formation, the presence of IgG4-related coronary periarteritis may not be recognized, even by invasive coronary angiography. Before reaching the conclusion of Komiya et al. that IgG4-related disease-associated coronary artery involvement may have a poor prognosis, we may have to accumulate more knowledge about the clinical course of and indication of steroid treatment for asymptomatic IgG4-related coronary periarteritis that is discovered incidentally, such as by pre-operative screening.

In addition, Komiya et al. stated that coronary bypass surgery has been performed in some cases where corticosteroid treatment was ineffective. However, whether corticosteroid therapy improves or aggravates the prognosis of IgG4-related coronary periarteritis has not been established, and the mechanisms involved remain unclear as well. At present, steroid therapy should not be officially recommended as a therapy to slow aneurysm formation and improve the luminal narrowing or IgG4-relarated inflamed coronary artery. To address this issue in the future, we should pay attention to both symptomatic and asymptomatic IgG4-related coronary periarteritis cases and carefully follow-up the clinical courses in such cases. Komiya et al.'s case report undoubtedly adds new information regarding the effect of steroid therapy for a patient with asymptomatic IgG4-related coronary periarteritis.

The author states that he has no Conflict of Interest (COI).