The Misdiagnosis of Beta-Thalassemia Heterozygosity Led by Hyperthyroidism

Likhasit Sanglutong; Somchai Insiripong; Wattana Insiripong

doi:10.33165/rmj.2022.45.3.256975

Authors

Likhasit Sanglutong Department of Medicine, Bangkok Hospital Muangraj, Ratchaburi, Thailand
Somchai Insiripong Department of Medicine, Saint Mary's Hospital, Nakhon Ratchasima, Thailand
Wattana Insiripong Department of General Practice, Nopparat Rajathanee Hospital, Bangkok, Thailand

DOI:

https://doi.org/10.33165/rmj.2022.45.3.256975

Keywords:

Hyperthyroidism , Fake Beta, Thalassemia, Heterozygosity

Abstract

When patients have mild microcytic hypochromic anemia with slightly increased hemoglobin (Hb) A₂ fraction, the most likely diagnosis is beta-thalassemia heterozygosity. But herein we found a patient who had all these hematological parameters but did not have beta-thalassemia heterozygosity. He was a 14-year-old Thai who presented with fatigue and heat intolerance for 2 weeks. His physical examination revealed mild diffuse enlargement of thyroid gland. Blood tests showed Hb 120 g/L, mean corpuscular volume (MCV) 72.1 fL, mean corpuscular hemoglobin (MCH) 23.3 pg/cell, free triiodothyronine (FT₃) > 20 pg/mL, free thyroxine (FT₄) > 5.0 ng/dL, thyrotropin < 2.5 mIU/L, serum ferritin 51.3 µg/L, Hb A₂ 3.8%. Besides primary hyperthyroidism, he was diagnosed with beta-thalassemia heterozygosity. After being treated with antithyroid drug for 6 months, his blood tests showed subclinical hyperthyroidism, Hb 146 g/L, MCV 83.3 fL, MCH 26.3 pg/cell, Hb A₂ 3.0%. Not only the thyroid hormones levels but also the Hb concentration, MCV, and the Hb A₂ percentage became normal. Due to this inconsistency, the DNA analysis for beta-thalassemia genes was performed and found negative for numerous common and rare beta-thalassemia genes meanwhile beta-globin gene sequencing appeared normal. It should be concluded that hyperthyroidism could induce slightly elevated Hb A₂ percentage and mild hypochromic microcytic anemia in a normal individual, leading to the misdiagnosis of beta-thalassemia heterozygosity. In other words, Hb analysis should not be performed during hyperthyroidism and it should be delayed till achievement of the euthyroid stage.

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