ATP1A1 and familial primary hypomagnesemia: LoF pathogenic variants of ATP1A1 result in different entities, including Charcot–Marie–Tooth 2 DD (CMT2DD, OMIM 618036), hypomagnesemia accompanied by seizures and cognitive delay (HOMGSMR2, OMIM 618314), complex spastic paraplegia (CSP), borderline learning impairment/sleep disorders/poor emotional control, and severe developmental delay/focal seizures.