A population‐based study of X and Y chromosome variations estimated that UPD of the X chromosome has a population prevalence of 1 in 47,305 women.[77] On ES we previously found this case to have an LP variant in SCN1A (c.3886T>A, chr2‐166866312‐A‐T, p.S1296T)[7] that may explain SUDP.[5] Pathogenic SCN1A variants have been associated with SIDS[7] and sudden unexpected death in epilepsy (SUDEP).[78, 79, 80]. The gene discussed is SCN1A; the disease is epilepsy.