NOTCH4 and fibromyalgia: Fibromyalgia has been genetically linked to the HLA region (6p21.3) 63, which includes several genes associated with Notch signalling (e.g. Notch4, FKBP5, TNXB, MTCH1 and TNF-a) or with stem cell maintenance and proliferation (e.g. POU5F1, Flot1, MAPK14, Rgl2 and Rab44).