Anomalous alterations affecting microglia in the central nervous system of a fetus at 12 weeks of gestation: case report


We report here on the first documented case of profound alterations specifically affecting the microglial population within the nervous system during the fetal period. This case, derived at gestational week 12, was one amongst a series of second trimester brains currently being investigated with respect to microglial colonization of the human fetal brain. No significant pathological alterations could be identified upon gross macroscopy or following microscopic analysis of serial brain sections stained with cresyl fast violet (Nissl). By contrast, sections stained immunohistochemically to detect MHC class II (CR3/43) and CD68 (PG-M1) antigens revealed a marked pathological change in the morphology and density of microglia within the CNS. Specifically, labeled cells within the rostral telencephalon were clearly hypertrophied and emitted numerous, branched processes in all directions, appearing in an atypical ‘hyper-ramified’ state uncharacteristic of microglia found in normal brains at this age. However, cells located elsewhere in the CNS (for example in the thalamus and internal capsule) appeared in a less differentiated state (small, rounded cells lacking processes) when compared to those within normal age-matched control brains. The total density and distribution of these labeled cells far outnumbered that seen in normal development. As far as we are aware, such an anomaly specifically affecting microglia, has not been documented previously. Consequently, this case represents the first of its kind, and the remarkable observations outlined in this study bear considerable significance from a neuropathological standpoint for future investigations into pathological changes affecting microglia in the central nervous system during the fetal period.

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The authors would like to thank Dr. U. Saretzki (Department of Pathology, Klinikum Schwerin, Germany) for human fetal material. Sabine Cleven, Anke Sund, Jana Müller and Frank Neudörfer are gratefully acknowledged for expert technical support.

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Correspondence to Payam Rezaie.

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Rezaie, P., Bohl, J. & Ulfig, N. Anomalous alterations affecting microglia in the central nervous system of a fetus at 12 weeks of gestation: case report. Acta Neuropathol 107, 176–180 (2004).

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  • Ramified fetal microglia
  • MHC class II antigen
  • CD68
  • Immunohistochemistry