Moreover, the paradoxical increased plasma ALP activity, which is a marker of bone turnover, in association with reduced plasma concentrations of CTX and P1NP, which are markers of bone resorption and bone formation respectively, in the NfixDel2/Del2 mice suggests additional extraskeletal origin for the raised ALP activity such as the kidneys or intestine, but not liver as mice, in contrast to humans, express little or no ALP in the liver,(41) and a search for additional renal or intestinal abnormalities in MSS may be warranted. Here, CYP27A1 is linked to Marinesco-Sjogren syndrome.