[Hereditary persistence of fetal Hb and its association with Hb S. 1st case found in Costa Rica]

An electrophoretic pattern of Hb S + Hb F, the relative concentration of this last being 37%, was found in a phenotypically mestizo 3 year-old child of Costa Rica. The genotype of the child was G gamma/A gamma, with a ratio of 1:1. Both hereditary alterations were disperse, according to the family study performed, which showed Hb S plus hereditary persistence of foetal haemoglobin of the African type G gamma A gamma (delta beta o). This case is briefly discussed, along with the molecular heterogeneity of HPFH and the importance of the differential diagnosis of electrophoretic patterns found in Hb S + Hb F patients.