Examples of this have been reported for ABCA4. For instance, the variant c.5603A > T (p.Asn1868Ile) was presented in STGD patients four times more frequently than expected (Zernant et al., 2017), and it is a disease-causing variant in 5% of patients when it is in trans with a severe allele in ABCA4. This variant was initially considered benign, however, recent studies consider it pathogenic with reduced penetrance (Zernant et al., 2017; Cremers et al., 2018; Runhart et al., 2018). The gene discussed is ABCA4; the disease is severe early-childhood-onset retinal dystrophy.