Long COVID neuropathy: The role of mast cells.

Abstract

Postacute sequelae of SARS-CoV-2 infection (PASC), or Long COVID, is estimated to affect over 60 million individuals globally, with almost half of COVID-19 survivors experiencing persistent symptoms such as neuropathic pain, fatigue, and autonomic dysfunction. Despite its prevalence, the pathophysiology of PASC remains poorly understood. This narrative review highlights activation of mast cells (MCs), the unique tissue immune cells as a central contributor to neuropathic manifestations in PASC. Mast cell locations near nerves and vessels allows them to regulate neuroimmune and neurovascular processes. Mast cell activation mirrors patterns seen in small-fiber neuropathy and myalgic encephalomyelitis/chronic fatigue syndrome, suggesting a shared immune-mediated etiology. The SARS-CoV-2 spike protein has been shown to activate MCs via angiotensin-converting enzyme 2 and toll-like receptor 4, triggering release of pro-inflammatory and neurotoxic mediators, including interleukin-1β, interleukin-6, tumor necrosis factor alpha, histamine, and tryptase. Such mediators sensitize peripheral nerves, disrupt the blood-brain barrier, and recruit microglia, ultimately contributing to small-fiber injury, neuroinflammation, and dysautonomia. Emerging reports suggest benefit from MC-directed treatments although responses remain variable. Understanding the role of MCs in PASC may offer a plausible mechanism of pathogenesis and guide targeted therapies. Future studies are needed to validate these findings and improve PASC patient outcomes.