Follow-up of five patients with FHHNC due to mutations in the Paracellin-1 gene.

Familial hypomagnesemia, hypercalciuria and nephrocalcinosis (FHHNC) is a rare autosomal recessive inherited disorder that has recently been attributed to a defect in the paracellin-1 ( PCLN-1)gene, encoding for a protein responsible for the tubular reabsorption of magnesium and calcium. Limited information is available on clinical course, therapy and prognosis. We provide information on five patients with FHHNC and their follow-up at our institution. Polyuria, nephrocalcinosis and hyperuricemia were the main clinical findings of a diagnosis at a median age of 4.4 years. The clinical course of PCLN-1 mutations as presented in this study is highly variable, ranging from compensated renal failure to end-stage renal failure - as happened in two of our patients. The progression to renal failure cannot be deduced from the initial presentation. Medical treatment does not appear to influence the progression of the disease. Despite calcium and magnesium substitution, normal values could not be achieved in these patients. Early treatment with vitamin D and calcium was essential to maintain growth. Adequate treatment allows for a normal height and pubertal development.