ABCA4 and severe early-childhood-onset retinal dystrophy: Recently, it was determined that c.2588G>C (p.[Gly863Ala, Gly863del]) only acts as a penetrant pathogenic variant when present in cis with c.5603A>T (p.Asn1868Ile).15 The common p.(Asn1868Ile) variant was found as a second ABCA4 allele in up to 50% of monoallelic STGD1 cases and is strongly associated with late-onset STGD1.15 Upon Haloplex-based ABCA4 gene sequencing, we found p.Asn1868Ile as a single variant in trans with other (potentially) causal variants in 25/65 (38%) of probands, who had an average age at onset of 42 years.