Dysregulation of an immune cell appears to underpin specific symptoms in patients with long Covid, researchers have said.

Tests on blood samples from 142 patients with long Covid who had been hospitalised and were then attending outpatient clinics showed patterns of malfunctioning of monocyte cells that was particularly linked to breathless and fatigue.

Writing in the European Respiratory Journal, the researchers from Manchester University said the abnormal features of circulating monocytes they found when compared with healthy volunteers could have ‘profound implications’ for the understanding of long Covid.

And the findings may provide novel opportunities for therapeutic targeting in Covid-19 patients with persistent symptoms, they concluded.

Their analysis showed that in long Covid, there was abnormal migration of monocytes that corresponded to shortness of breath in this group of patients.

Long Covid patients with ongoing breathlessness and abnormal chest X-ray tended to have high monocyte expression of a specific chemokine receptor as well as preferential migration of the cells towards the corresponding target in the lung.

A different migration pattern and expression profile of monocytes was seen in patients reporting fatigue.

The same dysregulation was not seen in those recovering from RSV or flu, the researchers said.

Dr Elizabeth Mann, study lead and researcher at the University of Manchester, said: ‘There is now a wealth of evidence indicating that chronic morbidity persists in many Covid-19 patients during convalescence manifesting as long Covid which remains a global public health problem despite vaccination programmes and milder strains of SARS-CoV-2.

‘These debilitating symptoms including extreme fatigue, shortness of breath, myalgia, brain fog, depression, fibrotic lung disease and pulmonary vascular disease and we now know this can last for many months or even years following infection.

But she added treatment options for long Covid were currently limited and the development of targeted therapeutics needed an in-depth understanding of the underlying immunological pathophysiology.

Dr Mann said: ‘Our work finding a link between monocyte function and specific long Covid symptoms may provide an important first step on the road to possible treatments.’

Dr Emily Fraser, consultant in respiratory medicine at Oxford University Hospitals NHS Foundation Trust, said it was important to note this was research done in a specific group of patients.

She added: ‘This is a post-hospitalised group of patients who would have had pneumonia and many probably have abnormal imaging subsequently related from Covid pneumonia lung damage.

‘Although they may have long Covid symptoms, most people with long Covid who were not hospitalised have no evidence of ever having had pneumonia and have normal lung imaging.’

A version of this article was first published by Pulse