ASS1 and Schnyder corneal dystrophy: For example, the top SNP associations one of the strongest correlates to chronological age, citrulline, mapped to coding regions for rate‐limiting enzymes of the urea cycle: carbamoyl phosphate synthetase 1 (CPS1) (Figure 4c, LocusZoom—previously associated with persistent pulmonary hypertension (Kaluarachchi et al., 2018), a common comorbidity in SCD) and argininosuccinate synthetase (ASS1) (Figure 4h), the latter part of the citrulline‐NO cycle.