Abstract Background Leukemia is the most common malignancy in children, while type 1 diabetes mellitus (T1DM) is one of the most prevalent autoimmune diseases among children. The etiology of both conditions is still largely unexplained, yet emerging evidence suggests certain similarities in environmental exposures and genetic predispositions. In this case-series, we sought a new potential factor behind the co-occurrence of leukemia and T1DM by thoroughly reviewing the medical records of patients diagnosed with both diseases. Methods We conducted a retrospective case series at Tampere University Hospital, Finland, by identifying pediatric patients diagnosed with both acute leukemia and T1DM from 1990 to 2023 using (International Classification of Diseases-10th revision) ICD-10 codes. Clinical and laboratory data, including leukemia subtype, age at diagnosis, treatments, comorbidities, and medical history, were collected, reviewed and analyzed descriptively. Study protocol was locally approved, and patient health data privacy was respected. Results Among 12 initially identified cases, seven met the inclusion criteria. Five cases were diagnosed with B-cell acute lymphoblastic leukemia (B-ALL), one with T-cell ALL (T-ALL), and one with acute myeloid leukemia. The mean age at leukemia diagnosis was 8.7 years (range from 0.7 to 15.3), while the mean age at T1DM diagnosis was 11.8 years (range from 7.5 to 17.8). In five cases, leukemia preceded T1DM, with two cases linked to asparaginase-induced pancreatitis. In two cases, T1DM developed before leukemia. Additional comorbidities included Down syndrome, Sotos syndrome, celiac disease, epilepsy, and Sweet’s syndrome. Conclusion This case-series presents findings, which align with previous observations (e.g., Down syndrome, pancreatitis), though a less often reported finding, Sotos syndrome, was also observed.
Rosti et al. (2026) studied this question.