More recently, retinal disease has been reported in patients carrying SPTLC1 variants.23 This clinical heterogeneity has been linked to the differing effects of each variant on SPTLC1 enzyme-substrate preference,20 and we observed similar differences in substrate utilization across the variants that we had studied at the enzymatic level (Figure 3A). The gene discussed is SPTLC1; the disease is Abnormal retinal morphology.