Since Van Bogaerts published the first case of CTX in 1937 (Gallus et al., 2006) over 118 different mutations implicated in CTX patients have been currently identified in CYP27A1 gene (NM000784.4) according to the Human Gene Mutations Database (HGMD) (Figure 3). Here, CYP27A1 is linked to cerebrotendinous xanthomatosis.