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Updated: Mar 27, 2026

Characterization of Sickling During Controlled Automated Deoxygenation with Oxygen Gradient Ektacytometry
Published on: November 5, 2019
A laboratory puzzle in a "blue" adolescent: Cyanosis, discordant oxygen measurements, and interference in leukocyte
Lianhui Yu1, Zhongjie Yang2, Liyuan Dai3
1Department of Laboratory Medicine, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China.
Abstract:
Methemoglobinemia caused by hemoglobin M variants is a rare inherited hemoglobinopathy characterized by lifelong cyanosis and discordant oxygen measurements. We report an 18-year-old male presenting with marked cyanosis, chocolate-brown blood, markedly reduced arterial oxygen saturation, normal arterial partial pressure of oxygen, and elevated methemoglobin levels. Complete blood count analysis on a Sysmex XN hematology analyzer revealed a global downward shift of fluorescence signals on the leukocyte differential scattergram with apparent pseudoeosinophilia, whereas parallel analysis on an ADVIA 2120 analyzer showed a normal leukocyte differential. Peripheral blood smear examination demonstrated no morphologic abnormalities. Hemoglobin electrophoresis and whole-genome sequencing identified a heterozygous HBB:c.190C > T (p.His64Tyr) mutation, confirming the diagnosis of Hb M Saskatoon-associated methemoglobinemia. This case highlights methemoglobin as an important but underrecognized source of analytical interference in fluorescence-based leukocyte differential analysis and underscores the need for integrated interpretation of scattergram features, cross-platform verification, and clinical context in automated hematology testing.
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