NR0B1 and alternating hemiplegia of childhood: This condition is inherited in two forms, either through autosomal recessive inheritance—for example, due to mutations in steriodogenic factor-1 (NR5A1)—or more commonly through X-linked inheritance.1–4 The X-linked form of AHC is due to a deletion or mutation in the gene encoding DAX1 (NR0B1) and is associated with hypogonadotropic hypogonadism.4 X-linked AHC may occur in isolation or as part of a contiguous gene deletion syndrome at Xp21 including genes for Duchenne muscular dystrophy (DMD) and glycerol kinase deficiency (GKD).