familial primary hypomagnesemia with normocalcuria familial primary hypomagnesemia with normocalciuria and normocalcemia Familial primary hypomagnesemia with normocalciuria and normocalcemia (FPHNN) is a form of familial primary hypomagnesemia (FPH), characterized by low serum magnesium (Mg) values but inappropriate normal urinary Mg values (i.e. renal hypomagnesemia). The typical symptoms are weakness of the limbs, vertigo, headaches, seizures, brisk tendon reflexes and mild to moderate psychomotor delay. ICD10:E83.4 MONDO:0018101 Orphanet:34527 SCTID:725031005 UMLS:C4510731 UMLS:CN204443