MECP2 and atypical Rett syndrome: This is largely due to the cell‐specific expression of heterozygous MECP2 variants and mosaicism due to X inactivation.[119] Several case studies have reported patients with Rett syndrome presenting with precocious puberty, suggesting a dual role for MECP2 in regulating the GnRH neuroendocrine network and socio‐behavioral neuronal circuits.