The questions chronic illness research is opening up
Support can start with how symptoms affect a day while clinical questions remain open.
When several symptoms arrive together, it can be difficult to explain them across separate appointments. Researchers are investigating possible links between muscles, nerves, immunity and pain. Some findings are early; they do not yet tell us which tests or treatments fit one person.
What is going on
Deconditioning Doesn’t Explain the Muscle
Long COVID and ME/CFS muscle tissue was tested directly against muscle made deliberately unfit. It didn’t match.
Movement scientist Rob Wüst and colleagues at Vrije Universiteit Amsterdam compared muscle tissue and blood from long COVID and ME/CFS patients against healthy volunteers who had spent sixty days in bed as part of a spaceflight simulation, a way of manufacturing deconditioning on purpose. Published in Nature Communications, the long COVID and ME/CFS muscles showed abnormalities in muscle fibre type, energy production, and oxygen supply that the deliberately deconditioned comparison group simply didn’t have.
→The muscle tissue was tested against manufactured deconditioning, and it didn’t match.
Hypermobility Has a Genetic Signature Beyond Collagen
Hypermobile Ehlers-Danlos syndrome was long filed under "loose collagen". The genome says the immune system is involved too.
A 2026 study combined machine learning with genome analysis across 86 people with hypermobile Ehlers-Danlos syndrome (hEDS, a connective tissue condition marked by joint hypermobility) and their unaffected relatives, screening over 35,000 genetic variants across more than 13,000 genes. HLA and immune-related gene variants turned up in 74% of patients. A separate genome-wide association study of over 1,800 hEDS cases pointed the same direction: a condition built on immune and connective tissue signalling together, not collagen genes alone.
→The genes involved reach past the joints and into the immune system.
The Dizziness Has a Nerve Fibre Count
Around half of POTS patients turn out to have measurable nerve loss, not an overly anxious nervous system.
Postural orthostatic tachycardia syndrome (POTS) causes the heart rate to spike and blood pressure to swing on standing up. Roughly half of POTS patients turn out to have small fibre neuropathy, damage to the fine nerve fibres that regulate blood vessels and sweat glands, confirmed on skin biopsy. A 2026 clinical review in Muscle & Nerve maps management for exactly this subtype, while newer research is testing corneal confocal microscopy, a scan of nerve fibres at the front of the eye, as a faster route to the same finding.
→Half of POTS looks less like anxiety and more like a nerve fibre count that can be measured.
Mast Cell Activation Syndrome Finally Has a Working Definition
MCAS spent years catching patients labelled "somatising". A six-year review of its diagnostic criteria says it’s working.
Mast cell activation syndrome (MCAS) occurs when mast cells, immune cells that release histamine and other chemicals, fire too easily and too often, producing allergic-type symptoms across multiple organ systems without an obvious trigger. A June 2026 review of the Consensus-2 diagnostic criteria, six years after their introduction, found they are correctly catching patients previously dismissed as somatising or handed a primary psychiatric diagnosis instead, without the feared wave of overdiagnosis. Some patients with real mast cell activation still fall outside even these criteria, but the direction is toward more accurate diagnosis.
→Six years of data say the criteria are finding real patients, not manufacturing new ones.
Fibromyalgia’s Brain Fog May Run Through the Gut
The gut and the brain share a direct communication line, and fibromyalgia research is starting to test it.
Fibromyalgia causes widespread pain alongside "fibro fog", the memory lapses and mental cloudiness that make concentrating difficult. A 2026 scoping review of the gut microbiome in fibromyalgia found a consistent pattern of altered gut bacteria in patients compared with controls, alongside early trials testing probiotics and other microbiota-targeted treatments for their effect on pain and cognition, not just digestion. The gut and brain share direct neural and immune signalling routes, which gives "the gut is involved" an actual pathway instead of a loose theory.
→The fog and the gut may be running on the same line, not two unrelated complaints.
What this could mean in practice
So what helps?
A measurable mechanism changes what’s worth asking for, not only what’s worth believing.
These findings raise questions for further research. A clinician can help decide whether a test is appropriate for your symptoms and history. For your appointment, a record of what happens, when, and what it prevents you from doing may be useful.
"The right test for this hasn't been run yet"
Describe the symptoms and how they affect you. Ask which investigations, if any, would be useful in your circumstances.
Energy tracking stays useful even while the exact mechanism behind a crash is still being mapped by researchers.
Symptoms that seem to belong to separate specialists (joints, gut, nerves, brain) may share one underlying system.
A short record of symptoms, timing and the effect on your day can help you prepare for an appointment.
Sources
- VU Amsterdam: Muscle problems in post-COVID and ME/CFS are not caused by prolonged inactivity
- Nature Communications: Skeletal muscle properties in long COVID and ME/CFS differ from those induced by bed rest
- Genes (MDPI): Multi-System Genetic Architecture of Hypermobile Ehlers-Danlos Syndrome
- Muscle & Nerve: Management of Small Fiber Neuropathy, a Clinical Perspective
- Afrin et al., PubMed: Progress in mast cell activation syndrome, the global consensus-2 diagnostic criteria at six years
- Journal of Orthopaedic Case Reports: Implications of Gut Microbiome in Fibromyalgia, a Scoping Review