The phenomenon of mosaicism was prevalent in neurodevelopmental diseases, such as Dravet syndrome and PCDH19‐related epilepsy.15, 26, 27 In the family of A065, two siblings were both diagnosed with AHC carrying the same pathogenic variant c.2401G>A/p.(Asp801Asn), however, this variant was not detected in father's blood. The gene discussed is PCDH19; the disease is epilepsy.