IgG4-related disease (IgG4-RD) is a systemic inflammatory disease characterized by marked infiltration of IgG4-positive (+) plasma cells into affected organs, but the concept of this disease has only recently been established. Coronary vasculitis is a rare disease that can cause sudden death, and it has recently been reported that IgG4-RD may be associated with vasculitis, including periarteritis and coronary disease. In this paper we report an autopsy case of sudden death of a man in his thirties, in which coronary periarteritis with features of IgG4-related periarteritis was detected. IgG4-RD was suspected from the presence of the following histopathological features: (1) markedly thickened adventitia and marked infiltration of the adventitia and periarterial fat by lymphocytes and plasma cells; and (2) infiltration of IgG4-positive plasma cells (ratio of IgG4+ cells to IgG4+ cells of >40 %, 50 IgG4+ plasma cells per high-power field) on immunostaining. The etiology and pathophysiology of IgG4-RD and IgG4-related periarteritis are still unclear, and further investigation of these conditions and their association with coronary lesions is needed. Careful consideration should be given to the possible presence of IgG4-RD when forensic pathologists encounter cases of sudden death accompanied by coronary periarteritis.