Although it is unknown how changes in this enzyme's function lead to the signs and symptoms of infantile neuroaxonal dystrophy, phospholipid metabolism problems have been seen in both this disorder and a related disorder called pantothenate kinase-associated neurodegeneration. These disorders, as well as the more common Alzheimer disease and Parkinson disease, also are associated with changes in brain iron metabolism. Researchers are studying the links between phospholipid defects, brain iron, and damage to nerve cells, but have not determined how the iron accumulation that occurs in some individuals with infantile neuroaxonal dystrophy may contribute to the features of this disorder.[citation needed]