Pathogenic variants in COL4A3, COL4A5 and COL4A5 result in XL (COL4A5) and AR Alport syndrome (where there are two COL4A3 or COL4A4 variants) which are characterised by kidney failure, sensorineural hearing loss and lenticonus, recurrent corneal erosions and a fleck retinopathy, retinal thinning and macular holes [42]. The gene discussed is COL4A3; the disease is Alport syndrome.