HMOX1 and alpha thalassemia spectrum: In addition, 21 of the 27 case-control studies evaluated the influence of various genetic variants on the risk of albuminuria and/or proteinuria: APOL1 (n = 10), MYH9 (n = 2), HMOX1 (n = 9), alpha-thalassemia (n = 9), BCL11A (n = 3), NPRL3 (n = 1), Duffy (n = 5), eNOS (n = 2), HbS haplotypes (n = 3), and others (n = 6).