Figure 2. Pathologic findings including results of external examination, histological features of central nervous system, and immunohistochemical staining in a fetus from a woman in French Guiana who was found to be infected with Tonate virus. A) External examination of the body showing subcutaneous edema, microcephaly, craniofacial malformations (short forehead, flat midface), and severe arthrogryposis with upper and lower limb malformations with joint contractures. B) Histologic view of brain section stained in hematoxylin and eosin, displaying lateral ventricle enlargement (asterisk), meningeal hemorrhage (long arrow), diffuse calcifications (short arrows), and nodular heterotopia (arrowheads). Scale bar = 3 mm. C) Spinal cord section showing an abnormally shaped and atrophic spinal cord with the presence of siderophages (sign of premortem meningeal hemorrhage, arrow). Scale bar = 1 mm. D) CD68 immunohistochemistry demonstrating microglial activation and small clusters of microglia and macrophages in the brain (hematoxylin counterstain). Scale bar = 1 mm. E–G) Immunohistochemistry, using anti-TONV mouse serum, of patient (E), control (F), and negative control (G) brains. Note the strong staining of many positive cells in the patient (arrows and inset in panel E), compared to the control brain, where a moderately diffuse background signal is shown but without strong positive cells such as in the patient. In the negative control (without anti-TONV mouse serum antibody), there is a very slight staining (arrowheads and inset in panel G) in the same cells compared with those in the patient, indicating the background signal (color trapping) in these cells. Scale bars = 300 μm; insets in panels E and G = 20 μm.