Neutropenia related to an azathioprine metabolic disorder induced by an inosine triphosphate pyrophosphohydrolase (ITPA) gene mutation in a patient with PR3-ANCA-positive microscopic polyangiitis

A 68-year-old Japanese man was monitored for chronic kidney disease (CKD), with unknown primary disease starting in 2014. His serum creatinine (sCr) was stable at ~ 2.5 mg/dL for ~ 2 years. Two weeks before admission, he had bloody sputum, and sCr increased to 4.63 mg/dL. Soon after admission, the patient developed a high fever with pigment spots on the legs. A kidney biopsy was performed. The kidney specimens showed necrotizing and crescentic...