Primary hypomagnesemia with secondary hypocalcemia (PHSH) is a form of familial primary hypomagnesemia (FPH, see this term), characterized by severe hypomagnesemia and secondary hypocalcemia associated with neurological symptoms, including generalized seizures, tetany and muscle spasms. PHSH may be fatal or may result in chronic irreversible neurological complications. The disease is Orphanet rare-disease nomenclature entry Orphanet_30924 (Primary hypomagnesemia with secondary hypocalcemia). Also known as: HOMG1, HSH, Hypomagnesemia caused by selective magnesium malabsorption, Hypomagnesemia intestinal type 1, Intestinal hypomagnesemia with secondary hypocalcemia, PHSH.