Many Sjogren’s patients are told they have fibromyalgia, without anyone ever considering the possibility of a Sjogren’s diagnosis. Sjogren’s symptoms can look a lot like fibromyalgia. Fibromyalgia is a diagnosis of exclusion. Once Sjogren’s is diagnosed, the “fibromyalgia” label should be dropped. Fibromyalgia is a syndrome, not a disease (181). It is cluster of symptoms that is not associated with objective markers. On the other hand, Sjogren’s is a well-characterized immune-mediated disease, not a syndrome. While Sjogren’s is not always easy to diagnose, there are numerous biomarkers (indicators) of the disease. The name “Sjogren’s syndrome” is inappropriate and outdated, and is slowly being replaced with “Sjogren’s disease” or simply, “Sjogren’s” (188).
A fibromyalgia diagnosis should prompt clinicians to look for Sjogren’s and other connective tissue diseases
Widespread pain, fatigue, brain fog, and trouble sleeping are symptoms that define fibromyalgia when there is no other explanation. Almost everyone with Sjogren’s experiences some, if not all, of these symptoms. Because so few clinicians have been trained to recognize even obvious Sjogren’s presentations, Sjogren’s remains vastly underdiagnosed. Diagnosis requires much more than a few blood tests. Negative antibody tests such as SS-A do not rule out Sjogren’s.
Nearly all Sjogren’s patients with “fibromyalgia” have been shown to have a neurological disorder called small fiber polyneuropathy (SFPN) (184,185). Neurologic features often precede a Sjogren’s diagnosis by many years. About 50% of Sjogren’s patients who present with neurological features such as SFPN are seronegative (SS-A negative) (178,179). Many do not have sicca symptoms that would prompt a Sjogren’s evaluation. They often experience especially long delays to diagnosis. Peripheral neuropathies are common, direct systemic manifestations of Sjogren’s.
For more information about SFPN and "fibromyalgia", watch Dr. Khosro Farhad's lecture.
Small fiber polyneuropathy (SFPN): pain, fatigue, and brain fog
SFPN refers to any condition that damages the small unmyelinated nerves in widespread areas of the body. SFPN is very common and underdiagnosed in Sjogren’s (184). Painful SFPN symptoms cannot be clinically distinguished from fibromyalgia symptoms (183). Dysautonomia in Sjogren’s is almost always caused by a type of SFPN that impacts the autonomic nerves. It is usually called “dysautonomia” for short, rather than the more precise “SFPN of the autonomic nerves”. Dysautonomia may contribute to fibromyalgia-like symptoms, especially fatigue and brain fog. Few rheumatologists are trained to recognize and treat dysautonomias. This is unfortunate because dysautonomia is a treatable cause of fatigue. Sjogren’s patients are often told that their fatigue is caused by fibromyalgia (186). Brain symptoms such as chronic daily headaches and cognitive dysfunction may also be caused by neuropathic dysregulation. This may be at the root of brain fog that is so often blamed on depression and fibromyalgia (184).
How is SFPN diagnosed?
Standard neurological examination and nerve conduction studies are normal in SFPN (178,179). However, these common tests can be helpful to rule out other types of neuropathy that can impact the myelinated nerves in Sjogren’s. Specialized tests such as a skin biopsy for nerve density, quantitative sensory tests, and autonomic tests are needed to diagnose SFPN. Patients with SFPN may be told that they don’t have a neurologic condition because clinician training and specialized testing are not the norm. See Dr. Oaklander’s video, Small fibers/big pain for more detail about diagnosis and treatment of SFPN.
This is a microscopic picture of unmyelinated nerve fibers (top) vs. myelinated nerve fibers. Myelin helps the nerves conduct electrical signals faster. Damage to myelinated nerves, but not unmyelinated nerves, can be detected by nerve conduction studies.
How does SFPN impact Sjogren’s patients?
Severe fatigue, widespread pain, and brain fog are the most disabling aspect of Sjogren’s for most patients (98,169,187), even when organ system involvement or lymphoma occurs (187, table 5). These general systemic features are probably the result of some combination of sensory SFPN, immune dysfunction, and dysautonomia. These are systemic manifestations of Sjogren’s, not caused by sicca or part of a "sicca syndrome".
Despite evidence that these general systemic features have a biological basis, patients with sensory SFPN and dysautonomia are often told that they have “fibromyalgia” or “functional neurologic disorder”. Many patients are told that their symptoms are caused by depression, anxiety or menopause. While all three may coexist with Sjogren’s and worsen symptoms, they have been shown to be independent from the core biologic causes of general systemic symptoms (26, 86). Understanding the cause of these symptoms, rather than treating them dismissively or psychologizing them, is important to good Sjogren’s care.
What can clinicians do?
First and foremost, patients want to be seen and validated. It is important for clinicians to acknowledge the real struggle they experience with these disabling symptoms. Patients need to be evaluated and treated with the best tools available. The Sjogren's Clinical Practice Guidelines, Systemic and the video links below are a good place to start.
While better tools for managing pain, fatigue, and brain fog are needed, rheumatologists and neurologists can start by learning more about both sensory SFPN and dysautonomia. Proper diagnosis and treatment of these conditions may provide substantial symptom relief.
Many long-haul COVID patients are now seeking care for a similar array of complex neurological features. Like Sjogren’s patients and people with ME/CFS, they have a difficult time getting diagnosed and treated for these life-altering conditions. The health care system is not meeting the clinical needs of either group. Clinicians need to ask that better resources for neurologic testing for SPFN/ dysautonomia be made available in their health care systems.
Please see glossary for unfamiliar terms.
Citations may be accessed at www.Sjogrensadvocate.com
Resources from Neuropathy Commons, MGH nerve unit
Video Lecture- Dr. Ann Louis Oaklander: Small fibers/ big pain
Video Lecture- Dr. Khosro Farhad: Fibromyalgia and Small Fiber Neuropathy