When Unstable Hemoglobin Lansing Interacts with Alpha Thalassemia Along with HbS: An Interesting Case with Unique Clinical Presentation.

Hemoglobin (Hb) Lansing is a rare mildly unstable variant of α globin. Here, we report the first case of compound Hb Lansing/HbS coinherited with a single α thalassemia deletion (-alpha^3.7) in a 27-year-old woman. The patient exhibited moderate hemolytic anemia and low oxygen saturation by pulse oximetry, which failed to improve with supplemental oxygen. Notably, her oxygen saturation levels were normal by arterial blood gas. Capillary electrophoresis and high-performance liquid chromatography showed an HbS peak along with other abnormal peaks. Subsequent α globin gene sequencing revealed one copy of the -alpha^3.7 α-globin deletion and one copy of Hb Lansing variant in the alpha2-globin gene. Hemoglobin Lansing is known to cause spuriously low pulse oximetry. Additionally, the co-inheritance of the Hb Lansing and a single α thalassemia deletion may contribute to her moderate hemolytic anemia. The timely identification of hemoglobin variants is crucial for understanding the underlying cause when encountering unexpectedly low pulse oximetry, facilitating genetic counseling, and preventing unnecessary investigations and treatments. Further research is also needed to enhance our comprehension of the interactions among various hemoglobin variants; especially those associated with single a α thalassemia deletion.