Microglia
Research has discovered dystrophic (defective development) human microglia. "These cells are characterized by abnormalities in their cytoplasmic structure, such as deramified, atrophic, fragmented or unusually tortuous processes, frequently bearing spheroidal or bulbous swellings." The incidence of dystrophic microglia increases with aging. Microglial degeneration and death have been reported in research on Prion disease, Schizophrenia and Alzheimer's disease, indicating that microglial deterioration might be involved in neurodegenerative diseases. A complication of this theory is the fact that it is difficult to distinguish between "activated" and "dystrophic" microglia in the human brain.
Microglia
Although historically frequently used, the term "activated" microglia should be replaced by "reactive" microglia. Indeed, apparently quiescent microglia are not devoid of active functions and the "activation" term is misleading as it tends to indicate an "all or nothing" polarization of cell reactivity. The marker Iba1, which is upregulated in reactive microglia, is often used to visualize these cells.