For example (Pavlova et al., 2009), described a female patient with severe hemophilia A with extremely skewed X‐inactivation who had two brothers with Coffin Lowry syndrome (a severe X‐linked recessive neurodevelopmental disorder; resulting from a nonsense variant in exon 5 of the RSK2 gene at Xp22.2). The gene discussed is RPS6KA3; the disease is Coffin-Lowry syndrome.