TSPAN12 and Norrie disease: Norrie disease, FEVR, ROP and Coats disease are all thought to share a similar pathophysiological cause; there is inadequate activation of the norrin- > FZD4, LRP5/6, TSPAN12 signalling pathway resulting in insufficient beta catenin stabilisation and therefore abnormal expression of downstream genes responsible for normal retinal vascularisation and the maintenance of the blood retinal barrier (BRB) (MacDonald et al., 2009).