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.
Beth Stevens
Stevens has found that microglia play a role in synapse loss in a range of disease states, including West Nile virus infection and neurodegenerative diseases such as Alzheimer's disease, where synapse loss precedes neuron death. Microglia may contribute to disease both by phagocytosing synaptic material and activating neurotoxic astrocytes. Her research indicates that neurodegenerative diseases may represent a local reactivation of microglial pruning pathways that are beneficial during development but detrimental in the mature brain. Stevens has also identified microglia as a contributor to Rett syndrome progression. This is independent of MECP2 mutation, which is known to cause the disease.