These tests may have included: chitotriosidase measurements, white cell enzyme studies to exclude other lysosomal storage disorders, and fluorescent and electron microscopy of both bone marrow aspirate and liver biopsy specimens.28 Because of the difficulties with the filipin staining test, the most widely performed and accessible definitive diagnostic test is now the sequencing of the NPC1 and NPC2 genes. This evidence concerns the gene NPC2 and lysosomal storage disease.