A new international case series revisits the natural history of D-bifunctional protein deficiency, showing that survival into adolescence and adulthood is possible and that normal VLCFA levels do not exclude the diagnosis. Dr James Nurse speaks with Dr Unai Díaz-Moreno and Dr Spyros Batzios about expanding phenotypes, genotype–phenotype correlations, and the growing role of early genetic diagnosis.From Neonatal Encephalopathy to Adult Survival: Revisiting the Natural History of D-Bifunctional Protein Deficiency in a Multicentre International Case SeriesU. Diaz-Moreno, et alhttps://doi.org/10.1002/jimd.70118