One of the goals of diabetes treatment is to ensure longevity, and investigation of the causes of death is extremely important to develop treatment strategies to achieve this goal. Given that the treatment environment for patients with type 1 diabetes (T1D) is constantly changing due to societal changes and advances in treatment methods, the purpose of this study was to investigate the most recent causes of death among patients with T1D. Therefore, we created a cohort consisting of 477 adult patients with T1D who visited the Juntendo Hospital or Aso Clinic from June to October 2019 and extracted the deaths. Seventeen deaths were identified by the end of August 2023. Causes of death were classified into three groups: (1) sudden death and suicide, (2) infectious diseases (septicemia in patients with collagen disease), and (3) malignant tumors and aspiration pneumonia. The patients in group (1) included relatively young patients. The patients in group (2) were all on steroids for collagen disease, and group (3) was considered a common cause of death in the elderly. These results suggest that it is important to consider the possible causes of death in the context of the patient's background and select an intervention method.

When measuring hemoglobin A1c (HbA1c) using high-performance liquid chromatography (HPLC), the chromatogram may trigger suspicion of variant hemoglobin. We present the case of a 60-year-old man. When the patient was 50 years of age, HPLC showed an extra peak in the patient's HbA1c chromatogram (HLC-723 G8 and G9, Toso). Accordingly, variant hemoglobin was suspected. He was diagnosed with diabetes mellitus at 52 years of age. Subsequently, the patient did not visit our hospital for 8 years because he moved away. Upon his return, his HbA1c level was 6.1 % on HPLC (HLC-723 G11), but an enzymatic assay of the same sample yielded an HbA1c level of 8.6 %. Although HPLC showed no abnormal peaks, isoelectric electrophoresis showed abnormal bands. The globin gene was analyzed with the patient's consent, leading to a diagnosis of variant hemoglobin and hemoglobin Hoshida. This case shows that the results can differ depending on the glycohemoglobin analyzer that is used. This variability must be carefully considered during the diagnosis of variant hemoglobin.