Transient hypoalgesia after COVID-19 infection

INTRODUCTION: Loss of smell or taste are often-cited complications during COVID-19 disease, but there is no clear evidence for affection of the peripheral nervous system. METHODS: Here, we report a 48-year-old man presenting with persistent dysgeusia and hypoalgesia of the lower legs, hands, and cheeks after COVID-19 infection in Spring 2020. RESULTS: Upon clinical examination 7 months after the infection, the patient could not feel pain after pinprick stimuli. Quantitative sensory testing revealed increased thermal detection thresholds at the face but no changes at the foot. Electrical C-fiber stimulation elicited lower pain ratings at the distal leg compared with the proximal leg, but overall higher pain ratings than in healthy control subjects. The axon flare reaction in response to histamine and acetylcholine was almost absent with no pain sensation. Skin punch biopsy revealed a reduced intraepidermal nerve fiber density at the lower leg, and transient receptor potential vanilloid 1 and calcitonin gene-related peptide immunoreactivity were similar to a healthy control. Symptoms and positive tests improved 5 months later. CONCLUSION: In summary, we describe a case of hypoalgesia after COVID-19 disease. Studies investigating long-COVID syndrome should test not only for painful neuropathic symptoms but also for hypoalgesia, especially in patients with prolonged dysgeusia.