HBA1 and phenylketonuria: Besides, Shi et al. also indicated the first two common recessive genes were HBA1/HBA2 and HBB (7.76% and 2.25%, respectively), and the next two common were PAH for phenylketonuria and SLC26A4 for autosomal recessive deafness 4 (2.18% and 2.03%)6.