Bi-allelic mutations in SLC34A3 cause HHRH, while heterozygous mutations in SLC34A1 and SLC9A3R1 cause the phenotypically similar hypophosphatemic nephrolithiasis/osteoporosis syndromes (NPHLOP1 and NPHLOP2, respectively). The gene discussed is SLC34A1; the disease is hereditary hypophosphatemic rickets with hypercalciuria.