[Early hypomagnesemia, hypercalciuria and nephrocalcinosis: two cases in a family]

Hypomagnesemia-hypercalciuria and nephrocalcinosis is a rare inherited syndrome which is characterized by persistent hypomagnesemia despite supplementation, hypercalciuria, nephrocalcinosis and progressive renal failure.

Case 1. A girl was referred at the age of 18 months because of polyuria, polydipsia and vitamin-resistant rickets. There was hypomagnesemia, hypercalciuria and mild renal insufficiency; ultrasonography showed nephrocalcinosis. For two years, she received hydrochlorothiazide and the course of the disease was marked by a significant reduction of urine output and hypercalciuria, recurrent urinary tract infections and a progression toward chronic renal failure. Case 2. The brother of this child was investigated at the age of nine months because of polyuria and polydipsia. He also had hypomagnesemia, hypercalciuria and nephrocalcinosis. Renal function was initially normal. After two years on continuous treatment with hydrochlorothiazide, hypercalciuria decreased without deterioration of renal function. No signs of rickets were noted and nephrocalcinosis remained stable.

To our knowledge, these two patients are the youngest reported in the literature. The long-term deterioration of renal function is hazardous but rickets may be avoided by early administration of hydrochlorothiazide.