A 7-year-old girl (III-1 in Figure 1A) with jaundice, a firstborn female of healthy parents (Korean male and Vietnamese female) at 39 weeks of gestation, visited the Division of Endocrinology, Department of Pediatrics, Jeonbuk National University Hospital (Jeonju, South Korea), for evaluation of a persistent hemolytic anemia. The proband appeared chronically ill with yellowish skin color, icteric sclera, hepatomegaly, and splenomegaly on physical examination. The rest of the examination was unremarkable. She was born at 38 weeks by vaginal delivery, with a birth weight of 2,300 g and unremarkable perinatal history. She was admitted to the neonatal intensive care unit after birth due to a lethargic condition. She was diagnosed with fetomaternal transfusion with suspected HHA. She was transfused with packed red cells. As time went on, she became pale and bright yellowish skin discoloration progressively. There was no family history of hemolytic disease. On the date of birth, her initial investigations showed a hemoglobin level of 5.3 g/dl, mean cell volume of 122.7 fl, total leukocyte count of 29,780/mm3, platelets of 159,000/mm3, and reticulocyte percentage of 60.18%. Direct Coombs test result was positive. A peripheral blood smear test showed marked leucoerythroblastic reaction and atypical lymphoid cells (1%-2%). Total bilirubin level was 12.51 mg/dl (normal range, 0.2-1.2 mg/dl), of which direct bilirubin level was 0.94 mg/dl (normal range, 0-0.4 mg/dl). Her aspartate aminotransferase and alanine aminotransferase levels were 107 IU/l (normal range, 24-95 IU/l) and 22 IU/l (normal range, 6-40 IU/l), respectively. Based on signs and symptoms including mild to severe anemia, paleness, fatigue, yellow discoloration of skin (jaundice), and bone problems, thalassemia was suspected initially in the proband. Sanger sequencing for HBB and HBA1/2 was performed at the Green Cross Genome (Yongin, South Korea). As a result, heterozygous missense mutation (NM_000518.5: c.79G>A, p.Glu27Lys; rs33950507) of the HBB was detected in both the proband and her mother (II-2 in Figure 1A). Although her mother had the same heterozygous HBB gene mutation, she showed no hemolytic symptoms. Thus, the proband and her mother were diagnosed with beta thalassemia trait. This trait usually has no clinical manifestation. The proband has been receiving RBC transfusions 1-2 times a month since birth until recently. On the other hand, the reticulocyte count of the proband was 1.64% at the time of the PK activity measurement. The red cell count and hematocrit were 1.88 x 106/mul and 16.5%, respectively; thus, the absolute reticulocyte count was 30,832/mul and the approximate corrected reticulocyte count percent was 0.6%.
Because the proband's parents and other family members presented no clinical symptoms associated with HHA, genetic counseling and segregation analysis were additionally performed to identify other genetic causes besides the HBB gene.