The pathological culprit of neuropathic skin pain in Long COVID-19 patients: A case series

Cutaneous neurosensory symptoms have become increasingly reported findings in COVID-19; however, these virus-related manifestations are largely overlooked, and their pathology is poorly understood. Moreover, alterations of skin sensibility currently recognize no clear histopathology substrate. The purpose of this study was to provide pathology evidence of neurosensory skin system involvement in COVID-19 patients complaining of subjective neurological symptoms affecting the skin. Out of 142 patients, six long COVID-19 cases complaining of cutaneous subjective neurological symptoms assessed on an NTSS-6 questionnaire underwent histopathological and immunohistochemical analyses of skin areas affected by paroxysmal diffuse burning and itching sensations. Two patients also performed electroneurography examination. The histology investigation showed hypertrophic glomus vascular bodies with hypertrophic S100+ perineural sheath cells and adjacent hypertrophy of the nerve branches associated with increased basophil polysaccharide matrix. Electroneurography revealed disturbances of A-delta and C dermal neuronal fibers. The main limitation of this study consisted of a limited number of skin biopsy samples, requiring further investigation. Histopathology findings are consistent with hypertrophy of nerve endings, suggesting a condition such as "dermal hyperneury", a recently reported small nerve hypertrophy condition affecting sensory C fibers. Such a neuropathic basis could explain dysesthesia experienced by the patients, as previously described in postherpetic neuralgia.