Polymyalgia rheumatica refers to an inflammatory condition characterised by pain and stiffness in the muscles of various parts of the body predominantly affecting the shoulder, neck, and hip. Although the exact causes of polymyalgia rheumatica remain unknown, scientists believe that genetic predisposition coupled with age and environmental factors play a pivotal role in the development of this disorder.¹ 

On the other hand, fibromyalgia is a chronic disorder correlated to alterations in the neural pathways responsible for perceiving and transmitting pain. Individuals with fibromyalgia may experience pain in multiple parts of the body, often accompanied by additional symptoms.²

Introduction

Polymyalgia rheumatica (PMR) and fibromyalgia (FM) represent two distinct conditions that exhibit certain similarities. Notably, they share a common suffix – "myalgia", where "my-" means muscle and “-algia” refers to pain,³ emphasising the centrality of pain as a shared physical symptom. Despite pain being a common symptom, the development and treatment of these conditions differ, highlighting the significance of accurate diagnosis.

PMR primarily affects people above the age of 50, with those assigned female at birth (AFAB) being 2-3 times more prone to developing this condition. PMR was found to be more prevalent among individuals of Northern European ancestry and in Northern European countries. For instance, in Sweden, the incidence ranges from 34 to 50 per 100,000 individuals aged 50 years and above while in Norway, it increases to 113 per 100,000 individuals in the same age group every year. Conversely, the incidence in Italy decreases to 13 per 100,000 individuals.⁴ 

FM also demonstrates a higher prevalence in people with AFAB and with increasing age, though people from all age groups can be affected.⁵ In the United States, FM’s incidence was reported at 6.4%, while in Europe and South America, it ranged from 3.3% to 8.3%.²

A thorough understanding of these conditions is pivotal for distinguishing them and delivering appropriate medical care.

Polymyalgia rheumatica

PMR is related to immune system changes, characterised by an inflammatory response. The causes of these findings are not well understood but scientists have proposed genetic predisposition as a potential factor in the development of PMR. Additionally, certain infections, including pneumonia due to mycoplasma, parvovirus, and Epstein-Barr virus, as well as influenza vaccinations, seem to be linked to PMR pathogenesis. Diverticulitis, the formation of small patches inside the digestive tract that get infected, has also been associated with PMR.¹

Symptoms of polymyalgia rheumatica

The most common symptoms of PMR include:⁴

• Pain and stiffness bilaterally on the neck, shoulders, upper arms, hips, and thighs. The intensity of pain is the most in the morning, gradually improving throughout the day. This symptom may arise within a few days to two weeks and impact the quality of life of individuals, impairing their daily activities
• Fatigue
• Arthralgia (joint pain)
• Loss of appetite
• Weight loss
• Fever

Diagnosis

While there is no clear evidence for the diagnosis of PMR, especially since no obvious clinical manifestations are present, physicians evaluate each case on an individual basis. The consistent pain in the morning for a specific duration and stiffness around the shoulder or hip in people over 50 years of age are key indicators for PMR. Elevated inflammatory markers such as erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP), along with the absence of other plausible explanations for the symptoms, contribute to the diagnostic process.⁴

Additional criteria, such as negative tests for rheumatoid factors or antinuclear antibodies also require consideration. Imaging techniques like ultrasonography often reveal bursitis, an inflammatory state of the fluid-filled sacs in the hip or shoulder. Distal bicep tendinitis is commonly observed in PMR patients. Moreover, approximately 50% of patients with giant cell arteritis also present with PMR manifesting with distinct symptoms.⁴

Fibromyalgia

The chronic syndrome of FM is related to alterations in the brain and spinal cord’s processing of pain sensations. People with FM are often oversensitive to pain and may experience widespread aches throughout the body. The exact cause contributing to this state is not yet completely understood, but factors such as genetic predisposition, environmental influences, psychological factors and trauma seem to be associated with this syndrome. The findings detected in patients with FM demonstrated an underlying dysregulated neurotransmission of specific neurotransmitters, such as glutamate and dopamine. These abnormalities contribute to the central neoplastic pain, characteristic of FM.⁶

Symptoms of fibromyalgia

The most common symptoms of FM include:⁶

• Widespread pain and stiffness in both muscles and joints
• Fatigue
• Insomnia
• Mood disorders
• Sleep disturbances
• Intestinal irritability
• Cognitive dysfunction
• Anxiety
• Depression

Diagnosis

Clinicians still face difficulties in assessing and diagnosing FM cases, as 75% of people with this condition remain undiagnosed. The tissue arises largely from the lack of specific radiological or laboratory diagnostic techniques available for FM. Instead, clinicians typically go through the medical history of patients, considering accompanying cognitive or psychological symptoms.⁷

Recent diagnostic analytic techniques involving immunophenotyping methods revealed that a specific opioid receptor could be a potential biomarker for FM. Furthermore, responses to the FM Impact Questionnaire revised version (FIQR), which assists in evaluating the severity and extent of pain, could offer reliable insights for diagnosis.⁷

Generally, the key diagnostic criteria for FM include pain on both sides of the body above or below the waist, along with generalised pain persisting for at least three months. Additionally, individuals exhibit pain also upon palpation(touch)  in at least 11 out of 18 specific body sites.⁶

Treatment approaches

Polymyalgia rheumatica management

General guidelines and protocols are available to practitioners facilitating the effective and personalised management of PMR. Currently, pharmacological therapy with the use of corticosteroids serves as the primary treatment approach for PMR. Administration of steroids is initiated in low doses and may extend for an average duration of 1 to 2 years; although some patients require up to 4 years of treatment. However, for 29-45% of patients, this treatment is not adequate to relieve the symptoms with more than half of patients encountering adverse side effects of steroids. A relapse of the disease is also a plausible scenario which is typically managed with an increased dosage of steroid medication.⁸

Disease-modifying antirheumatic drugs (DMARDs), such as methotrexate, could also be used as an alternative option to corticosteroids, but are still under scrutiny for their efficacy on PMR. Further biologic and synthetic DMARDs are currently undergoing clinical investigation for their effectiveness, aiming to introduce additional treatment options, particularly for patients who exhibit an inadequate response or low tolerance to steroid treatment.⁸

Finally, auxiliary non-pharmacological interventions such as physiotherapy, diet, and personalised exercise regimens can also be beneficial in preserving muscle function and flexibility in patients with PMR.⁸

Fibromyalgia management

The enigmatic and multidimensional nature of FM poses challenges in its treatment, as no single pharmacological or non-pharmacological treatment has been identified to effectively treat this syndrome for all patients. With symptoms fluctuating over time,  the treatment of FM focuses on alleviating the symptoms and enhancing the overall quality of life. Management of FM is currently based on guidelines and recommendations proposed by the European League Against Rheumatism.⁹

Pharmacological treatment

Medications to manage the symptoms of FM include mostly pain medications and antidepressants, e.g. amitriptyline, monoamine oxidase inhibitors, selective serotonin reuptake inhibitors, and serotonin and norepinephrine reuptake inhibitors. These agents have demonstrated positive effects on pain reduction, sleep, fatigue, and overall emotional health, though their efficacy is not universal, and disadvantages may exist.⁹ The therapeutic potential of cannabis products is also supported by patient surveys and clinics. However, more clinical trials are needed to validate their effectiveness.¹⁰

Non-pharmacological treatment

Alternative therapies are recommended by physicians as important components for treating FM. These include:⁹

• Exercise: aerobic and resistance exercises were both significantly effective in improving pain and physical function
• Acupuncture: Acupuncture therapy has demonstrated improvements in pain and fatigue in patients, although supporting evidence of its effectiveness is still scarce
• Cognitive behavioural therapies (CBTs): CBTs have been associated with pain and disability reduction, with results maintained over the long term
• Other psychological and stress-reduction therapies

 Comparison of key aspects between PMR and FM

Conclusion

PMR and FM are distinct conditions with pain being the common symptom. PMR is an immune-mediated condition believed to be caused by genetic alterations, along with other infectious or inflammatory factors. It is mostly observed in people over 50 years of age, with symptoms such as morning pain and stiffness in the muscles of the hips, shoulders, and neck, often improving throughout the day. Diagnosis typically involves a comprehensive symptom assessment, along with laboratory tests and imaging techniques. Treatment for PMR is initiated with corticosteroids and is adjusted according to the patient’s response.

FM is a chronic syndrome characterised by widespread pain and tenderness in various parts of the body. Individuals with FM experience an augmented perception of pain related to alterations in the neuronal pain signalling pathways. Additional symptoms include fatigue, sleep disturbances, and cognitive changes. Treatment of FM is mainly symptom-specific, with the use of antidepressants and other non-pharmacological approaches such as exercise, and acupuncture.

It is crucial to seek medical help from certified specialists to properly diagnose and differentiate between PMR, FM, and other conditions. Discussing your symptoms in-depth and following the doctor’s recommendations for additional tests are essential for developing a tailored treatment plan that best suits your needs.