PAPSS2 and brachyolmia: Table 3 illustrates that in PAPSS2 deficiency, four different bone phenotype variants are observed: 1) overt SEMD with both vertebrae and long bones affected (n = 23); 2) overt brachyolmia with dysplastic changes confined to the spine (n = 15); 3) overt brachyolmia with dysplastic changes confined to the spine with additional minimal epimetaphyseal changes only visible on x-ray (n = 4); and 4) subclinical brachyolmia with radiological changes only, as observed in the first patient we described (4).