French national diagnosis and care protocol (PNDS) for infantile idiopathic hypercalcemia (IIH).

The objective of this study was to establish a French National Diagnosis and Care Protocol (PNDS: Protocole National de Diagnostic et de Soins), with the aim of providing health professionals with free, open access synthesis on optimal management and care of patients with Infantile Idiopathic Hypercalcemia (IIH) (https://www.has-sante.fr/jcms/p_3522489/fr/hypercalcemie-infantile-idiopathique-hii). The process involved a critical review of the literature and a multidisciplinary expert consensus. IIH is a rare genetic disorder, with a prevalence estimated at 1 in 33,000. Its clinical manifestations (such as urinary stones or nephrocalcinosis) can appear at different ages. The pathophysiology of IHH is characterized by excessive 1,25(OH)2 vitamin D mediated dietary digestive calcium absorption. The underlying mechanism varies depending on the pathogenic variant involved, which is located in one of two genes, CYP24A1 or SLC34A1. The natural history and pathophysiology of IHH remain poorly understood and are underreported in the literature. Management of the disease varies according to the presentation and severity of hypercalcemia. Non-specific management strategies encompass the cessation of calcium intake, the discontinuation of native vitamin D supplementation, hyperhydration, and the occasional utilization of bisphosphonates. The necessity for long-term treatment, which may encompass both non-specific measures and specific interventions, depends on the severity and the genetic variant identified. Long-term follow-up appears essential, although there is limited data available, particularly for detecting complications of the disease, with nephrocalcinosis being the primary one.