Many believe that reactive astrogliosis may occur as a graded response toward the type of CNS insult sustained, in which only certain facets of the changes associated with reactive astrogliosis are observed (i.e., increased GFAP expression without increased astrocyte proliferation), and this may explain potential differences when comparing the phenotypes of astrocytes between the different HE pathologies. The gene discussed is GFAP; the disease is hereditary elliptocytosis.