Markedly low hemoglobin A1c in a patient with an unusual presentation of beta-thalassemia minor.

Objective: To describe very low hemoglobin A1c levels in a patient with type 2 diabetes mellitus and an unusual presentation of beta-thalassemia minor.

Methods: We present the clinical and laboratory findings of the study patient.

Results: A 64-year-old African American man with type 2 diabetes mellitus was referred to the endocrinology clinic with a hemoglobin A1c level of 1.6% despite elevated blood glucose concentrations. A red blood cell survival study with chromium-51 revealed that he had a reduced erythrocyte life span less than 25% of normal. He also had a markedly elevated reticulocyte count ranging from 236 to 534 x 10(3)/microL (reference range, 25-75 x 10(3)/microL). The laboratory findings, which are not characteristic of beta-thalassemia minor, could be the cause of the markedly low hemoglobin A1c in this patient.

Conclusions: Although rare, when associated with marked erythrocyte turnover, beta-thalassemia minor can lead to a severe reduction in HbA1c levels. In this scenario, glycemic control is best assessed by measuring fructosamine.