Hereditary spherocytosis and the (TA)nTAA polymorphism of UGT1A1 gene promoter region--a comparison of the bilirubin plasmatic levels in the different clinical forms.

Hereditary spherocytosis (HS) is the most common nonimmune hemolytic anemia in individuals of northern European ancestry, affecting 1 in 2000 [1]. HS is classified as mild, moderate or severe according to the severity of the symptoms, family history and analytical presentation—hemoglobin (Hb) concentration, reticulocyte count and serum bilirubin levels [1]. When performing the classification of HS in our patients during the last years, we observed that bilirubin levels were sometimes inconsistent with the other parameters defining the severity of this anemia. This was particularly evident in some mild HS cases that presented unexpectedly high bilirubin plasma concentration, which was not in agreement with the other analytical parameters. A potential cause for this discrepancy could be the co-inheritance of HS and