The identification of blister, bite, and ghost cells on a blood smear as valuable clues for diagnosing G6PD deficiency in a 3-year-old child Author List: Zulin Xie1, Wei Li1, Xueyan Chen21. Department of Laboratory Medicine, Liuzhou People’s Hospital, Liuzhou, Guangxi2. Clinical Laboratory, Department of Clinical Laboratory, People’s Hospital of Longhua Shenzhen, Shenzhen, China, 518109.Corresponding author: Xueyan Chen Clinical Laboratory, Department of ClinicalLaboratory, The People’s Hospital of Longhua Shenzhen, Shenzhen, China. 518109,China. Fax: +86 755 27741585. E-mail address:13632546963 @163.comTo the Editor:Glucose-6-phosphate dehydrogenase(G-6PD) deficiency is the most prevailing enzyme defect in humans, affecting over 400 million individuals worldwide . The most prevalent life-threatening symptoms associated with G-6PD deficiency are acute hemolytic crises upon exposure to triggering factors like medications, infections, or consumption of fava beans. Managing acute hemolytic crises in patients without medical history of G-6PD deficiency often presents a significant challenge for hematologists and emergency department (ED) physicians. The identification of morphological abnormalities remains crucial for the differential diagnosis of hemolytic anemia . In certain cases, such abnormalities can only be determined through the examination of a blood smear.A 3-year-old boy was brought to the emergency department with generalized jaundice and hematuria after taking oral antipyretic ibuprofen one day ago. The physical examination revealed pale lips, indicating a glaring presence of severe anemia. Blood tests demonstrated severe microcytic anemia (icteric plasma, hemoglobin 43g/L, hematocrit 14.4%, mean corpuscular volume 75fl). The urine appeared to be a deep shade of red, showing the presence of occult blood (3+), and bilirubin (2+). Peripheral blood smear revealed the presence of considerable anisopoikilocytosis, blister cells (“hemi-ghost” cells) characterized by irregularly contracted hemoglobin from one side and half-empty cytoplasm), and occasional bite cells (Figure 1 ). Furthermore, ghost cells were observed, which are erythrocyte membranes devoid of hemoglobin (Figure 1 ). Further studies confirmed hemolysis with a high reticulocyte count (0.268×1012/L), increased unconjugated bilirubin (79μmol/L), increased lactate dehydrogenase (1475U/L), decreased haptoglobin (< 0.1 g/L). We strongly advised the emergency physician to consider the possibility that the patient was experiencing an acute hemolytic crisis stemming from G6PD deficiency. The patient was promptly admitted to the pediatric ward for a thorough examination. The direct and indirect antiglobulin tests yielded negative results, effectively ruling out the presence of immune-mediated acute hemolysis. However, the G6PD enzyme activity assay yielded normal results. A follow-up G6PD assay conducted six weeks after the patient’s discharge revealed a significantly reduced enzyme activity (148 u/L, reference range >1300 u/L), solidifying the clinical suspicion of G6PD deficiency in the patient. Meanwhile, a missense variant in exon 12: c.1466G>T (p. Arg 489Leu) (hemizygous) was detected in the G6PD gene as a pathogenic mutation reported in the literature [HGMD cm910163] (Figure 2 ).In our study, we noted a significant drop in hemoglobin levels within the initial 24 hours following the initiation of ibuprofen therapy in a child suffering from fever, accompanied by the emergence of hemoglobinuria and irregular red blood cell (RBC) morphology in the blood smear. Blood smears play a critical role in diagnosing this disorder due to two significant reasons. Firstly, it is considerably faster when compared to the results determined solely by the measured activity of G6PD. When taken into account alongside the patient’s ethnic origin and medical history, a preliminary diagnosis can be established. Secondly, in the case of a hemolytic crisis, it is important to note that even if the G6PD assay yields normal results, a diagnosis of G6PD deficiency can still be suggested through blood smears, as exemplified in the current case. The reason why C6PD deficiency exhibits normal assay results after an acute hemolytic crisis is that the abnormal cells tend to undergo lysis more readily, leading to a predominance of cells with the normal allele in the bloodstream . Hence, the identification of typical RBC morphological features in the blood smear suggests the need for multiple measurements of G6PD activity following the resolution of the acute hemolytic episode. Hemoglobinuria serves as a significant indicator of intravascular hemolysis and is a characteristic of drug-induced acute hemolysis in individuals with G6PD deficiency . In contrast, drug-induced acute hemolysis typically manifests as extravascular hemolysis without hemoglobinuria in patients with normal red blood cells.In conclusion, the diagnostic process was significantly aided by blood smear analysis, highlighting its crucial role in this particular scenario.