RESUMO
BACKGROUND: The wide variation in hemoglobin (Hb) F levels has been observed in patients with Hb EE disease. This study aimed to describe hematologic features and determine the effect of genetic variants on Hb F expression in young children with Hb EE disease. METHODS: Hematologic features and Hb profiles of Laotian children aged 6-23 months, who originally enrolled in the Lao-Zinc study, were retrospectively reviewed. Only children with Hb EE disease, as indicated by DNA analysis, were included in this current analysis. Genetic variants, including the G γ-XmnI polymorphism (C>T) of the HBG2 gene, the HBS1L-MYB intergenic region on chromosome 6, and the BCL11A on chromosome 2 as well as the mutations occurring on the Krüppel-like factor 1 (KLF1) gene, were examined. RESULTS: In total, 205 children were diagnosed as having Hb EE disease with Hb F ranged from 1.2 to 43.7%. Most of the children had mild to moderate anemia with a remarkable microcytosis. Analysis of the genetic variants revealed an extremely high frequency of the G γ-XmnI (93.7%). Applying multiple regression analysis adjusted for age, sex, and α-thal gene, a positive relation was observed for the rs4671393 (coefficient = 3.87, p = .005) and the rs2297339 (coefficient = 2.48, p = .046), but not the G γ-XmnI. A statistically non-significant relation was noted for the rs9399137 and the -154 (C>T) KLF1 mutation. CONCLUSION: Our findings provide insight into complex situation of Hb F variability in young children with Hb EE disease; and this can guide to appropriate care and counseling to affected families.