Mutations in PRPH2 (also known as TSPAN22 or RDS) and in ROM1 (also known as TSPAN23), which function together in stabilising the structure of photoreceptor outer segment discs, can cause retinitis pigmentosa (Kajiwara et al. 1994), while mutations in TSPAN12 can cause familial exudative vitreo-retinopathy type 5 (EVR5) (Poulter et al. 2010; Nikopoulos et al. 2010). The gene discussed is ROM1; the disease is retinitis pigmentosa.