When we sorted these listed variants by a conservation score (phyloP score) to identify those that were most likely to be functional, a novel missense variant in RRM2B (g.341G > A, p.P33S), whose rare, heterozygous variant had been known to cause adPEO, was ranked at the top (Table 2). The gene discussed is RRM2B; the disease is autosomal dominant progressive external ophthalmoplegia.