March hemoglobinuria progressed to acute kidney injury after kendo practice: a case report.

BACKGROUND: March hemoglobinuria is caused by a hemolytic mechanism due to transient hematuria after physical exercise which, although rare, may lead to acute kidney injury. We report a case of a patient with march hemoglobinuria induced by kendo, which was diagnosed by the presence of Berlin blue iron staining in the proximal tubules through renal biopsy. CASE PRESENTATION: A 15-year-old male complained of fever (37 °C), general malaise, and nausea after hard kendo sessions. Laboratory findings revealed indirect bilirubin dominant hyperbilirubinemia (total bilirubin 3.8 mg/dL), high lactate dehydrogenase (LDH), and acute kidney injury (serum creatinine: 3.11 mg/dL and estimated glomerular filtration rate: 26 mL/min/1.73m2). Urine test was positive for occult blood but without hematuria. Renal biopsy was performed to clarify the cause of renal injury, which showed minor glomerular abnormalities. Meanwhile, hemosiderin deposition was identified in the proximal tubules by Berlin blue iron staining, and lysosomes were observed to contain granular iron. In addition to clinical background of strenuous kendo exercise, renal biopsy led to a definitive diagnosis of march hemoglobinuria. CONCLUSIONS: March hemoglobinuria is a hemolytic disease that can occur after intense exercise, especially kendo. Considering its rarity due to the lack of critical symptoms, it is important to note that occult blood-positive findings may be indicative of march hemoglobinuria if the patient underwent strenuous exercise. Therefore, clinicians should be aware of this possibility to provide timely and appropriate treatment.