Martín-Martínez, Eva, Gil-Perotin, Sara, Giménez-Orenga, Karen et al. · International journal of molecular sciences · 2025 · DOI
This study describes one patient who had ME/CFS and was later diagnosed with multiple sclerosis (MS). Doctors discovered that his blood had unusual patterns of human endogenous retroviruses (HERVs)—ancient viral-like sequences in our DNA that can sometimes affect immune function. Importantly, this patient improved significantly after receiving rituximab, a treatment that modifies the immune system, even though standard treatments had not worked for him.
This case suggests that HERV dysregulation may play a role in ME/CFS and related autoimmune conditions, and that examining the full HERV landscape rather than single proteins might reveal new treatment targets. The dramatic response to rituximab in this patient adds to evidence that B-cell directed therapy merits further investigation in ME/CFS, potentially opening new therapeutic avenues beyond current standard approaches.
This is a single case report and cannot establish causation between HERV dysregulation and ME/CFS or MS symptoms. The study does not prove that the observed HERV profile was responsible for rituximab's effectiveness, nor does it demonstrate that other ME/CFS patients will have similar HERV profiles or treatment responses. The absence of elevated HERV-W ENV suggests other HERV elements may be relevant, but this remains speculative without larger cohort validation.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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