NPC1 and nasopharyngeal carcinoma: The main cause of NPC disease is the functional inactivation of NPC1 and NPC2 proteins due to mutations in the NPC1 and NPC2 genes, particularly in NPC1 gene located in chromosome 18q11, which accounts for up to 95% of cases of the disease (Carstea et al., 1993, 1997), while the remaining 5% are due to mutations in the NPC2 gene located on chromosome 14q24 (Naureckiene et al., 2000).