Falsely decreased HbA1c in a type 2 diabetic patient treated with dapsone

Glycated hemoglobin A1c (HbA1c) is an important indicator of glycemic control. The current recommendation for glycemic control based on HbA1c values has been widely accepted. However, HbA1c values depend on the lifespan of erythrocytes and the assay methods used. Here, we report the case of a patient with type 2 diabetes with unusual falling of HbA1c due to interference from dapsone treatment for leukocytoclastic vasculitis. He was a 52-year-old man, who was diagnosed with type 2 diabetes mellitus 5 years previously and who had been treated in our hospital in the past 3 years. Glycemia was controlled by sulfonylurea and metformin. During the 3-years follow-up period, HbA1c dropped significantly during the addition of dapsone treatment, although plasma glucose levels remained stable. HbA1c levels were raised after discontinuation of dapsone. With rechallenge of dapsone usage, HbA1c decreased again. We conclude that dapsone may be the cause of artificially low HbA1c. Other measurements to monitor glycemic control should be considered when dapsone is used for the treatment of concurrent disorders, such as autoimmune disease and pneumocystis jiroveci pneumonia.