UGT1A1 and cholelithiasis: In particular, the brother heterozygous for the Hb Southern Italy and homozygous for the UGT1A1 (TA)7 shows an acceptable level of bilirubin and absence of cholelithiasis, indicating that the co-presence of –α3.7 deletion increases the percentage of the unstable variant and thus the severity of the phenotype.