Cerebrotendinous xanthomatosis is a disorder characterized by abnormal storage of fats (lipids) in many areas of the body (lipid storage disease). People with this disorder cannot break down certain lipids effectively (such as cholesterol), so these fats form fatty yellow nodules called xanthomas, that accumulate in the body, especially in the brain and the tendons that attach muscle to bone, which is reflected in the condition name (cerebro- meaning brain and -tendinous referring to tendons). Symptoms may include diarrhea, clouding of the lens of the eyes (cataracts), tendon problems and progressive neurologic problems, such as epilepsy, movement disorders, impaired speech (dysarthria), loss of sensation in the arms and legs (peripheral neuropathy), dementia, hallucinations, and depression. Other symptoms may include brittle bones that are prone to fracture (osteoporosis) and an increased risk of developing heart or lung failure because of lipid buildup. It is caused by genetic changes in the CYP27A1 gene.