VIENNA — Fibromyalgia is increasingly recognized as a multidimensional, symptom-based condition rooted in altered central pain processing, rather than a disorder defined by structural pathology, said experts in a discussion at the 24th European Congress of Internal Medicine (ECIM) 2026.

Presenting an overview of the condition, Alina Dima, MD, PhD, a specialist in internal medicine and rheumatology at the Carol Davila University of Medicine and Pharmacy and Colentina Clinical Hospital, both in Bucharest, Romania, described fibromyalgia as a prototypical example of nociplastic pain.

“Fibromyalgia reflects altered pain processing in the absence of structural pathology, although it is likely a heterogeneous syndrome with potential peripheral and immune contributions in selected subgroups,” Dima explained. “It is one of the clearest examples of nociplastic pain, where the problem is not in the tissues themselves but in how the nervous system processes and amplifies signals.”

Dima also highlighted that there is an overlap between fibromyalgia and post-viral syndromes, including long COVID, with potential for nociplastic mechanisms across these conditions.

Physician-Dependent Model Shifts to Patient-Centered Framework

Earlier diagnostic approaches to fibromyalgia focused on tender-point examination, which became central to the 1990 classification criteria, but this approach has since been largely abandoned. “What was really being assessed was the pain response to palpation, not the points themselves,” Dima explained.

More recent diagnostic criteria reflect a shift toward patient-reported symptoms. Tools such as the Widespread Pain Index and Symptom Severity Scale now capture both the distribution of generalized pain and the broader symptom burden, including fatigue, unrefreshing sleep, cognitive dysfunction, and somatic complaints, she explained.

he complex relationship between fibromyalgia and post-viral syndromes, particularly long COVID, was also discussed. “There are similarities between long COVID and fibromyalgia in some patients,” Dima said, noting that both conditions lack specific biomarkers and may involve nociplastic mechanisms.

She added that there is also an overlap with myalgic encephalomyelitis/chronic fatigue syndrome, with some patients fitting a broader picture of post-viral central sensitivity syndromes. However, she stressed that these conditions should not be considered interchangeable.

“Long COVID is not always fibromyalgia,” she said. “In some patients [with long COVID], there are objective biological abnormalities, including immune changes, autonomic dysfunction, post-exertional worsening, and even organ-specific sequelae after the SARS-CoV-2 infection.”

These features suggest that while some patients may develop a fibromyalgia-like phenotype following viral illness, others have a distinct pathophysiologic process.

“The most accurate interpretation is partial overlap, not equivalence,” and “terminologies like post-COVID syndrome or post-acute sequelae of SARS-CoV-2 infection might be more appropriate in some cases than long COVID,” Dima said.

Diagnosis by Exclusion and Persistent Uncertainty

Fahad Ashraf, MD, a physician at Fiona Stanley Hospital and St John of God Midland Public Hospital, both in Perth, Australia, told Medscape News Europe that the diagnostic challenges described in fibromyalgia closely mirror those encountered in long COVID and chronic fatigue syndromes.

“Fibromyalgia is basically a diagnosis of exclusion,” he said. “There are quite a few overlapping syndromes, so we have to rule out all other obvious causes before we can label it as fibromyalgia.”

These may include post-viral syndromes such as long COVID, as well as endocrine, metabolic, or psychological contributors.

“Once you have a viral infection, there can be an immune response that affects how the body behaves,” Ashraf said. “That can trigger symptoms like fatigue, sleep disturbance, and difficulty concentrating, but those symptoms can also overlap with anxiety, depression, or other stress-related factors.”

The absence of a diagnostic test remains a major limitation. “There is no gold standard investigation to confirm the diagnosis,” he said. “It is based on exclusion.”

He described a case in which a patient referred with a diagnosis of fibromyalgia was ultimately found to have an alternative explanation for her symptoms. “When I reviewed her tests, I found she had elevated calcium levels,” he said. “Further investigation showed primary hyperparathyroidism caused by a small parathyroid tumor. Once that was treated, her symptoms improved significantly.”

Such cases highlight the risk for misdiagnosis if underlying organic causes are not fully explored. “Sometimes fibromyalgia can be a misdiagnosis if you haven’t done enough workup,” he said.

Managing the Diagnosis and the Patient

Ashraf emphasized that diagnosis is only part of the challenge; communicating it effectively is often even more difficult. “The hardest part is how you explain the diagnosis to the patient,” he said.He described an approach focused on validation and practical support. “I aim to be empathetic and acknowledge their symptoms, then give a tailored plan based on their situation,” he said, including addressing lifestyle factors, stress, and activity levels.

Exercise, he noted, plays a central role despite being counterintuitive for many patients. “When people are tired, they don’t want to exercise,” he said. “But it becomes a vicious cycle. You have to break that cycle. You have to be tired first to get rid of the tiredness.”

Ashraf recommends gradual, sustainable activity. “Even simple brisk walking is better than nothing,” he said. “It may take a few weeks, but patients can start to feel improvement.”

Dima added that despite broader diagnostic criteria, fibromyalgia remains difficult to recognize in practice, with ongoing uncertainty around both underdiagnosis and overdiagnosis, as well as how much investigation is needed before confirming the diagnosis.