Small fibre neuropathy frequently underlies the painful long-COVID syndrome, 2024, Falco et al.

[SNT Gatchaman]

Small fibre neuropathy frequently underlies the painful long-COVID syndrome
Falco, Pietro;Litewczuk, Daniel;Di Stefano, Giulia;Galosi, Eleonora;Leone, Caterina;De Stefano, Gianfranco;Di Pietro, Giuseppe;Tramontana, Lorenzo;Ciardi, Maria Rosa;Pasculli, Patrizia;Zingaropoli, Maria Antonella;Arendt-Nielsen, Lars;Truini, Andrea

Approximately 10% to 20% of individuals with previous SARS-CoV-2 infection may develop long-COVID syndrome, characterized by various physical and mental health issues, including pain. Previous studies suggested an association between small fibre neuropathy and pain in long-COVID cases.

In this case–control study, our aim was to identify small fibre neuropathy in patients experiencing painful long-COVID syndrome. Clinical data, quantitative sensory testing, and skin biopsies were collected from 26 selected patients with painful long-COVID syndrome. We also examined 100 individuals with past COVID-19 infection, selecting 33 patients with painless long-COVID syndrome, characterized mainly by symptoms such as brain fog and fatigue, and 30 asymptomatic post–COVID-19 controls. Demographic and clinical variables were compared among these groups.

Among the 26 patients with painful long-COVID syndrome, 12 had skin biopsy and/or quantitative sensory testing abnormalities compatible with small fibre neuropathy. Demographic and clinical data did not differ across patients with small fibre neuropathy, patients with painless long-COVID syndrome, and asymptomatic post–COVID-19 controls.

This case–control study showed that approximately 50% of patients experiencing painful long-COVID syndrome had small fibre neuropathy. However, in our patient cohort, this specific post–COVID-19 complication was unrelated to demographic and COVID-19 clinical variables. Approximately half of our sample of patients with painful long-COVID symptoms met diagnostic criteria for small fibre neuropathy.

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[rvallee]

I'm wondering if it'd be worth testing for this. I don't even know if it's worth doing, if it'd change anything. If I can even get it tested. If it's even a thing that they test around here.

I'm leaning towards... no. I may get a reference to a new (from last year) clinic dedicated to chronic illness, maybe they do that there. If I get an appointment before the end of the decade.

 

[SNT Gatchaman]

Of the 26 patients with painful long-COVID syndrome included in this study, 12 (47%) received a diagnosis of small fibre neuropathy. In these patients, pain was primarily distributed distally, and COMPASS-31 questionnaires detected autonomic symptoms, such as orthostatic intolerance.

patients with painful long-COVID syndrome were categorized into distinct sensory phenotypes using a QST-based algorithm designed for patients with peripheral neuropathic pain. These phenotypes represent specific combinations of sensory abnormalities, possibly reflecting different underlying mechanisms of neuropathic pain. Patients with small fibre neuropathy more frequently presented sensory loss and mechanical hyperalgesia profiles compared with those without

Eleven of the 14 patients with painful long-COVID syndrome without a diagnosis of small fibre neuropathy experienced widespread pain, accompanied by fatigue, waking unrefreshed, and cognitive symptoms, therefore meeting the diagnostic criteria for fibromyalgia syndrome.

Patients with painful post–COVID-19 symptoms, whether or not they had small fibre neuropathy, had similar demographic and clinical characteristics when compared with previously ill control participants without post–COVID-19 symptoms and those with painless post–COVID-19 symptoms. This argues against a previous study indicating that various clinical variables, including body mass index and COVID-19 severity, predict persistent neuropathic pain.

The discrepancy may be attributed to different study designs because our study specifically selected patients with small fibre neuropathy using diagnostic tests and widely accepted criteria. Therefore, our findings suggest that patients with painful post–COVID-19 symptoms should be screened for small fibre neuropathy regardless of COVID-19 severity or specific risk factors.