ABCA4 and severe early-childhood-onset retinal dystrophy: This identified a single previously reported pathogenic variant c.4685 T > C, p.(I1562T) [1], in the proband (II/2, Fig. 3), but a second variant was not identified; (at that time, 15–30% of STGD patients were reported as having only one detectable mutation in ABCA4 [2–4]).