Research Information System
60th60.th Annual Meeting of the European Society for Paediatric Endocrinology, Rome, Italy, 15 - 17 September 2022, vol.95, no.2, pp.150
Introduction: The SLC34A1 gene encodes the NaPi-IIa
cotransporter, which plays an important role in phosphate reabsorption in the kidney proximal tubule. Inactivating mutations of
this gene cause nephrolithiasis and osteoporosis, together with
clinical pictures such as hypophosphatemic rickets type 1, Fanconi
renotubular syndrome type 2, and infantile hypercalcemia type 2.
Case: A 40-day-old male patient presented with medullary
nephrocalcinosis and hypercalcemia. He was born at 35 weeks,
2660 g. It was learned that the patient had hyperechogenic kidneys
and oligohydramnios on antenatal ultrasonography (USG), and a
combined heterozygous mutation in the SLC34A1 gene was
detected in the amniotic fluid sample at the 21st gestational week.
There were no signs of developmental delay and dehydration in his
physical examination. At the time of admission, he had hypercalcemia, lower limit phosphorus level, increased alkaline phosphatase, low parathormone, and hypercalciuria. 25OHD level was
normal. In urinary USG, renal parenchyma echogenicity increase
and millimetric stones in the renal medulla were detected. 24-hour
urine protein level was normal, urine protein electrophoresis and
urine glucose were negative, and proximal tubulopathy was
excluded. Oral phosphorus solution at a dose of 30 meq/kg/day
was started. In the follow-up of the patient, hypercalcemia and
hypercalciuria regressed and returned to the normal range.
In the family screening of the patient, a novel variant in the
SLC34A1 gene was detected in the father {c.1256G>A (p.S419N)
(p.Ser419Asn)(heterozygous)} and mother {IVS6+1G>A
(c.644+1G>A)(heterozygous)}. The patient’s genetic result, clinical and laboratory findings were found to be compatible with
infantile hypercalcemia type 2. In his brother, crystalloid was
detected in his urinary USG, his laboratory values were normal and
he had no complaints. In the genetic analysis, the same variant
changes were detected in the same gene as the patient.
Conclusion: SLC34A1 mutation may present with different
clinical manifestations. Despite the absence of significant low
phosphate and phosphaturia in our case, success was achieved with
the phosphorus treatment that was initiated. Therefore, this mutation should be considered in children with hypercalcemia close to
the lower limit of normal or with slightly low phosphorus levels, as
in our case. Although the patient’s sibling has the same variant
changes, the fact that there is no hypercalcemia and only kidney
crystalloid can be considered that mutations in this gene may cause
a wide spectrum of disease.