Familial hypomagnesemia with hypercalciuria and nephrocalcinosis: report of three Turkish siblings

Familial hypomagnesemia with hypercalciuria and nephrocalcinosis: variable phenotypic expression in three affected sisters from Mexican ancestry

Familial hypomagnesemia with hypercalciuria and nephrocalcinosis is a rare autosomal recessive renal disease caused by mutations in genes for the tight junction transmembrane proteins Claudin-16 (CLDN16) and Claudin-19 (CLDN19). We present the first case report of a Mexican family with three affected sisters carrying a p.Gly20Asp mutation in CLDN19 whose heterozygous mother showed evident hypercalciuria and normal low magnesemia without any other clinical, laboratory, and radiological symptoms of renal disease making of her an unsuitable donor. The affected sisters showed variable phenotypic expression including age of first symptoms, renal urinary tract infections, nephrolithiasis, nephrocalcinosis, and eye symptoms consisting in retinochoroiditis, strabismus, macular scars, bilateral anisocoria, and severe myopia and astigmatism. End stage renal disease due to renal failure needed kidney transplantation in the three of them. Interesting findings were a heterozygous mother with asymptomatic hypercalciuria warning on the need of carefully explore clinical, laboratory, kidney ultrasonograpy, and mutation status in first degree asymptomatic relatives to avoid inappropriate kidney donors; an evident variable phenotypic expression among patients; the identification of a mutation almost confined to Spanish cases and a 3.5 Mb block of genomic homozygosis strongly suggesting a common remote parental ancestor for the gene mutation reported.

Bilateral slipped capital femoral epiphysis in a male adolescent with familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC), chronic renal failure, and severe hyperparathyroidism

Slipped capital femoral epiphysis (SCFE) is the most common orthopedic hip disorder affecting otherwise healthy adolescents. The majority of SCFE cases are classified as idiopathic; rarely, it may be secondary to different endocrinopathies including hyperparathyroidism due to chronic renal failure (CRF). However, over the last decades, the association between SCFE and CRF has almost disappeared, probably due to better management of renal osteodystrophy. Familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC, OMIM no. 248250) is a rare autosomal recessive tubulopathy characterized by renal wasting of calcium and magnesium leading to hypomagnesemia, hypercalciuria, nephrocalcinosis, and CRF. Patients usually show hyperparathyroidism before the onset of advanced CRF caused by FHHNC-related metabolic disturbances. We report on a 15-year-old patient with FHHNC and CRF who developed extreme hyperparathyroidism and high-grade bilateral SCFE after self-discontinuation of supportive treatment of underlying conditions.

CONCLUSION

We believe that SCFE was caused not only by untreated CRF but also by metabolic disturbances related to FHHNC. To prevent this complication, careful management of disturbances of calcium, phosphate, and magnesium homeostasis seems to be crucial.