Sarcoidosis is a granulomatous disorder of unknown etiology, with several clinical manifestations. Löfgren's syndrome is an acute type of sarcoidosis, characterized by the triad of arthritis, erythema nodosum, and bilateral hilar lymphadenopathy (BHL), which spontaneously resolve within about 2 years. Löfgren's syndrome is common among young white women from Nordic countries and Ireland, but it is very rare in Japan. Because the incidence of Löfgren's syndrome varies according to race, most studies on Löfgren's syndrome, including HLA typing, have been reported in Western countries. Indeed, HLA-DR3 has been reported to be associated with Löfgren's syndrome in Western countries, although the association between HLA typing and Japanese Löfgren's syndrome remains unclear. Here we present a Japanese patient with Löfgren's syndrome. A 34-year-old female patient was hospitalized with arthritis and erythema nodosum. Chest computed tomography revealed mediastinal and BHL. Endobronchial ultrasound-guided transbronchial needle aspiration showed non-caseating epithelioid cell granulomas. Löfgren's syndrome was thus diagnosed. Her ankle arthralgia and bilateral ankle swelling recovered without steroid treatment within two months, and the BHL almost completely diminished one year after admission. Her HLA genotype contains DR12. We also reviewed the literature on 11 Japanese patients with Löfgren's syndrome, showing that HLA-DR12 is present in five out of nine patients (55.6%). The relevant data were unavailable in the remaining three patients. Importantly, only 5.4% of registered donors in the Japan Marrow Donor Program are positive for this allele. We suggest the potential link between HLA-DR12 and the pathogenesis of Löfgren's syndrome in Japanese patients.