In 57% of all MD/CCRD cases (77% of the 185 solved cases), retinal disease was explained by mutations in ABCA4 (n = 94, 37%), PRPH2 (n = 29, 12%) or BEST1 (n = 19, 8%; including 5 a.r. and 14 a.d. mutations). This evidence concerns the gene BEST1 and Menkes disease.