PMC9876709_01
May-Giemsa staining of a blood smear showed red blood cells (RBCs) of different sizes, including microspherocytes (arrows, x400) (a). A flow cytometric osmotic fragility test showed an extremely low number of remaining RBCs. Whole blood was added to hypotonic saline and incubated. Each gate represents the remaining RBCs at each time point within 5 minutes. The percentage of residual red cells was calculated based on the following formula: [(cell number of Gate B+C)/2]/cell number of Gate A x0.6 (b). In the eosin-5 -maleimide binding ability test, fluorescent signals were decreased among all RBCs. The x-axis shows the signal strength of eosin-5 -maleimide-labeled RBCs. The histogram of the patient's sample is shown in black, and that of the normal control is shown in yellow (c). Small RBCs were gated by their different sizes (d), and their fluorescent signals were further diminished.
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A peripheral blood smear showed RBCs of various sizes, including microspherocytes (Fig. 1a). The calculated percentage of residual red cells was also extremely low at 11.0% (reference range, 46.0-68.8%), which indicated decreasing osmolality resistance of RBCs (Fig. 1b). In the eosin-5 -maleimide binding ability test, fluorescent signals were decreased to 21.5 mg/dL RBC (reference range, 21.8-27.0 mg/dL RBC) among all RBCs (Fig. 1c). Upon gating smaller RBCs (Fig. 1d), their signals were even further diminished to almost 18.0 mg/dL RBC.
A heterozygous mutation of c.2161G>A (p.E721K) in SPTA1 was identified (a). A homozygous polymorphism of c.211G>A (p.G71R) in UGT1A1 (UGT1A1*6) was also identified (b).
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As a result of these analyses, a heterozygous mutation of c.2161G>A (p.E721K) in the SPTA1 gene was identified (Fig. 2a). We also identified homozygous polymorphism of UGT1A1*6 by sequencing (Fig. 2b).