Hereditary hypophosphatemic rickets with hypercalciuria and nephrolithiasis—Identification of a novel SLC34A3/NaPi‐IIc mutation

Hereditary hypophosphatemic rickets with hypercalciuria (HHRH) is characterized by rickets, hyperphosphaturia, hypophosphatemia, elevated 1, 25-dihydroxyvitamin-D, increased gastrointestinal calcium absorption and hypercalciuria. Serum calcium, 25-hydroxyvitamin-D and PTH levels are normal. Here we describe a boy with HHRH, nephrolithiasis, and compound heterozygosity for one previously described mutation (g. 4225₅0del) and a novel splice mutation (g. 1226G>A) in SLC34A3, the gene encoding the renal sodium-phosphate co-transporter NaPi-IIc. The patient's mother and grandmother are carriers of g. 4225₅0del, and both have a history of nephrolithiasis associated with hypercalciuria and elevated 1, 25-dihydroxyvitamin-D. His three siblings (2-6 years old), who are also carriers of g. 4225₅0del, have hypercalciuria but so far their renal ultrasounds are normal. Thus, SLC34A3/NaPi-IIc mutations appear to be associated with variable phenotypic changes at presentation, which can include recurrent nephrolithiasis.