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. 4225_50del) and a novel splice mutation (g. 1226G > A) in SLC34A3, the gene encoding the renal sodium-phosphate cotransporter NaPi-IIc. The patient's mother and grandmother are carriers of g. 4225_50del, 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. 4225_50del, 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. (C) 2011 Wiley-Liss, Inc.