A rare yet deadly autoimmune disorder appears to be on the rise in the north of England, and new research indicates that the outbreak may be linked to COVID-19. Known as Anti-MDA5 positive dermatomyositis, the disease was mainly observed in Asian populations prior to the pandemic, yet is now surging among the caucasian residents of Yorkshire.

Triggered by antibodies that attack an enzyme called MDA5 (melanoma differentiation-associated protein 5), the illness is associated with progressive interstitial lung disease, which is characterized by scarring of the lung tissue. Between 2020 and 2022, doctors in Yorkshire reported an unprecedented 60 cases of MDA5 autoimmunity, resulting in eight deaths.

Analyzing this surge in a new study, the researchers point out that the sudden increase in cases coincides with the major waves of COVID-19 infections during the peak years of the pandemic. This immediately grabbed their attention because MDA5 is an RNA receptor that plays a key role in recognizing the SARS-CoV-2 virus.

“Here we report a surge in the rate of anti-MDA5 positivity testing in our region (Yorkshire) in the second year of the COVID-19 pandemic, which was notable because this entity is relatively rare in the UK,” write the study authors. This phenomenon, they say, is probably indicative of “a distinct form of MDA5+ disease in the COVID-19 era,” which they have labelled “MDA5-autoimmunity and Interstitial Pneumonitis Contemporaneous with COVID-19” (MIP-C).

To understand the mechanisms underlying this newly-identified symptom, the researchers used data-crunching tools that seek out shared traits among members of medical cohorts. In doing so, they discovered that patients with MDA5 autoimmunity tended to also have high levels of an inflammatory cytokine called interleukin-15 (IL-15).

Commenting on this finding in a statement, study author Pradipta Ghosh explained that IL-15 "can push cells to the brink of exhaustion and create an immunologic phenotype that is very, very often seen as a hallmark of progressive interstitial lung disease, or fibrosis of the lung."

Overall, only eight of the 60 patients had previously tested positive for COVID-19, suggesting that many may have had asymptomatic infections that they weren’t aware of. This implies that even mild infections that produce no initial symptoms may be sufficient to trigger MDA5 autoimmunity.

“Given the peak of MDA5 positivity testing followed the peak of COVID-19 cases in 2021, and coincided with the peak of vaccination, these findings suggest an immune reaction or autoimmunity against MDA5 upon SARS-CoV-2 and/or vaccine exposure,” conclude the researchers. 

According to Ghosh, the phenomenon is unlikely to be restricted to Yorkshire, and reports of MIP-C are now coming in from all over the world.

The study has been published in the journal eBioMedicine.