UGT1A1 and hereditary spherocytosis: However, the distribution of subjects with respect to UGT1A1 genotypes was similar to that found in previous studies involving Portuguese children with Hereditary Spherocytosis, with a 7/7 frequency of 8.8%(28), as well as Portuguese healthy subjects, with frequencies observed in two studies of 6.3 and 9.9% [28], [31].