Background: Immunotherapy is a novel treatment which is associated with autoimmune side effects. The risk though of autoimmune diabetes is quite low, occurring in only 0.2-1.0% of patients, and most cases occur following PD-1 rather than PD-L1 inhibitor use. To date there are no prior reports of autoimmune diabetes developing in the setting of immunotherapy in a patient of Indigenous background whom are most susceptible to type 2 diabetes. We report a unique case following atezolizumab use, which is a PD-L1 inhibitor.
Case Presentation: A 55 year old Indigenous female was commenced on atezolizumab for recurrent squamous cell lung carcinoma. There was no history of diabetes, thyroid disease and autoimmune disease. Prior to its commencement random blood sugar levels (BSLs) ranged between 4.8 – 7.9 mmol/L and HbA1c was 5.1%. Two months following atezolizumab use, there was the onset of fatigue, polyuria, polydipsia and new hyperglycaemia with random BSLs up to 10.9 mmol/L. Subsequently she was found to have borderline low C-peptide levels of 0.6 nmol/L (0.5 – 1.0 nmol/L), and positive zinc transporter 8 (ZnT8) antibodies with undetectable glutamate acid decarboxylase and islet tyrosine phosphatase 2 antibodies. Following the diagnosis of autoimmune diabetes, she was commenced on low dose lantus which maintained BSLs between 5 – 7 mmol/L and resolved her symptoms of hyperglycaemia. Although atezolizumab is thought to have led to the development of autoimmune diabetes, it was initially continued with close oncology and endocrinology follow-up.
Conclusion: There are few case reports of atezolizumab-induced autoimmune diabetes, and we present the first case associated with ZnT8 antibodies. In addition this case is also unique in that it occurred in a patient of Indigenous background.