Familial primary hypomagnesemia with hypercalciuria and nephrocalcinosis with severe ocular involvement (FHHNCOI) is a form of familial primary hypomagnesemia (FPH), characterized by excessive magnesium and calcium renal wasting, bilateral nephrocalcinosis, progressive renal failure and severe ocular abnormalities. The disease is Monarch Disease Ontology entry MONDO_0009548 (renal hypomagnesemia 5 with ocular involvement). Also known as: FHHNC with severe ocular involvement, FHHNCOI, Meier-Blumberg-Imahorn syndrome, bilateral macular coloboma with hypercalciuria, familial hypomagnesemia with hypercalciuria, nephrocalcinosis and severe ocular involvement, hypercalciuria-bilateral macular coloboma syndrome.