Numerous variants of the SMPD1 gene, along with variability in residual ASM activity and other genetic/epigenetic factors, result in a spectrum of ASMD disease severity from a uniformly fatal form with death occurring by 3–4 years of age (ASMD type A or infantile neurovisceral ASMD previously known as NPD A) to chronic forms characterised by visceral (ASMD type B or chronic visceral ASMD, previously NPD B) and neurovisceral disease (ASMD type A/B chronic neurovisceral ASMD, previously NPD A/B) (Table 1) [5,6,7]. Here, SMPD1 is linked to anterior segment dysgenesis.