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Case presentation
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A 41-year-old male with a past medical history of hemolytic anemia as a neonate presented to the emergency department with diabetic ketoacidosis. Although he was lost to follow-up since birth, he reported excessive thirst, weight loss, and malaise six months prior to the ketoacidosis episode. He was treated at a regional hospital where his HbA1c was 7.6% and blood glucose level was 670 mg/dL. He also presented with systemic jaundice, increased indirect bilirubin, hemolytic anemia, liver cirrhosis, and poorly controlled diabetes mellitus. After multiple days of treatment (including insulin), he was discharged with instructions to follow up with an endocrinologist.
At his post-discharge visit, his serum ferritin was markedly high (3,642 ng/mL). Magnetic resonance imaging (MRI) revealed findings compatible with hemochromatosis, showing iron deposits in organs such as the liver, pancreas, and pituitary. The diagnosis of hemochromatosis was confirmed via liver biopsy showing prominent iron depositions and liver fibrosis. The patient also had evidence of multiple organ failure.
After family history and genetic testing (PIEZO1 gene mutation) further confirmed hereditary hemochromatosis, the patient was given an oral iron-chelating agent (deferasirox 20 mg/kg/day). His ferritin decreased to 1,640 ng/mL over 3 months. However, the prolonged iron overload was thought to impair his pancreatic beta-cell function, leading to the diabetes diagnosis.
For diabetes management, the patient was treated with insulin and dietary counseling. Continuous and self-monitored blood glucose was measured, giving a 205 mg/dL average. This corresponds to a theoretical (calculated) HbA1c of 8.8%; however, his measured HbA1c was 6.1%.
Due to this discrepancy, the patient's glucose was closely monitored over 30 days. The measured HbA1c was significantly lower than the estimated HbA1c according to the two-tailed paired t-test (p< 0.001).
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Study Author Conclusions
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This is a case report of a patient with dehydrated hereditary stomatocytosis and a PIEZO1 gene mutation complicated by diabetes mellitus and liver cirrhosis due to hemochromatosis. Although continuous glucose monitoring and self-monitored glucose monitoring were conducted, the values did not match up with laboratory-measured A1c values. The formula used to estimate HbA1c was the A1c-Derived Average Glucose (ADAG) Study Groups formula: average glucose level (mg/dL)=28.7×HbA1c (%)-46.7.
In patients with hemolytic anemia, the HbA1c is falsely low because of the shortened erythrocyte survival. Chronic liver disease and chronic renal failure also affect the HbA1c level. As such, average glucose levels may be more useful for evaluating glycemic control than HbA1c if the latter is affected by coexisting conditions that shorten or prolong the mean erythrocyte lifespan.
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