Fig. 1.

Chest X-ray showing massive COVID-19 pneumonia in a middle-aged male patient (A), who developed an acute carpal and cubital tunnel syndrome after SARS-CoV-2 infection in the non-dominant limb; macroscopically, a whitish color of the median nerve is well noticeable during decompressive surgery (B). On microscopy, small nerve collaterals are in myxoid degeneration (C, hematoxylin & eosin, 20× objective), well highlighted by histochemistry, which stains mucins in light blue (D, Alcian Blue, 20× objective). Immunohistochemistry for S100 protein labels in brown the nerve collaterals through diaminobenzidine as chromogen (E, clone 4C4.9, Ventana Medical Systems, 20× objective), while immunohistochemistry for SARS-CoV-2 nucleoprotein does not reveal any positivity in the excised tissue, to suggest an indirect effect of viral infection (F, clone FIPV3-70, Santa Cruz Biotechnology, 20× objective).