Development of Acute Promyelocytic Leukemia in a Patient with Granulomatosis with Polyangiitis: A Case Report

Granulomatosis with polyangiitis (GPA) is a rare disorder of unknown etiology, which is characterized by necrotizing granulomatous inflammation of the upper respiratory system and kidneys. Immunosuppressive treatment (cyclophosphamide or azathioprine with glucocorticoids) improved the outcome of GPA, however, latent comorbidity (cancers and hematologic malignancies) has become more prevalent in recent years. Here, we present a first case of the patient with GPA complicated by acute promyelocytic leukemia (APL) successfully treated with molecular-targeted therapy. A 77-year-old female was referred to our hospital for nasal obstruction, hearing loss, and fever. Otorhinolaryngological investigation revealed otitis media, and head computed tomography (CT) showed paranasal mucosal thickening with septal perforation. Chest CT showed cavitary granulomatous lesions in both lungs. Biopsy of the nasal mucosa revealed granulomatous lesions, and the patient was finally diagnosed with GPA. Oral administration of prednisolone 50 mg/day was initiated, and oral azathioprine (50 mg/day) was added. After 26 months of azathioprine initiation, pancytopenia developed and azathioprine was stopped. Then sudden elevated levels of blasts appeared in the hemogram (blasts 11%). She was diagnosed with APL via bone marrow examination which revealed plenty of faggot cells with Auer rods and chromosomal mutation. The patient was started on all-trans retinoic acid 60 mg/day following arsenic trioxide 7 mg/day in consideration of elderly onset. Complete remission was achieved and oral prednisolone was successfully reduced to 15 mg/day without a major relapse of GPA. Because GPA can be complicated by APL even during maintenance treatment using azathioprine, careful monitoring should be performed in such patients.