Isoform 1 and isoform 3 are widely expressed with highest levels in retina and testis, with isoform 1 being the mot abundant in all tissues tested. Involvement in disease:Defects in FAM161A are the cause of retinitis pigmentosa type 28 (RP28) . A retinal dystrophy belonging to the group of pigmentary retinopathies. Retinitis pigmentosa is characterized by retinal pigment deposits visible on fundus examination and primary loss of rod photoreceptor cells followed by secondary loss of cone photoreceptors. Patients typically have night vision blindness and loss of midperipheral visual field. As their condition progresses, they lose their far peripheral visual field and eventually central vision as well.