From the Guidelines
The exact cause of polymyalgia rheumatica (PMR) remains unknown, but it is believed to result from a complex interplay of genetic predisposition, environmental triggers, and immunological factors, with a strong association with giant cell arteritis (GCA) 1. The condition appears to involve an abnormal immune response that leads to systemic inflammation, particularly affecting the shoulders, hips, and neck.
- Age is a significant factor, as PMR rarely occurs in people younger than 50 and becomes increasingly common with advancing age, peaking in the 70s and 80s.
- There is a genetic component, with certain HLA (human leukocyte antigen) genes, particularly HLA-DR4, associated with increased susceptibility.
- Some evidence suggests that viral or bacterial infections may trigger PMR in genetically predisposed individuals. The disease shows a strong association with GCA, with approximately 15-30% of PMR patients developing GCA, suggesting shared pathogenic mechanisms 1. Seasonal variations in PMR onset have been observed, further supporting the role of environmental triggers. The inflammatory process in PMR involves activation of dendritic cells, T-cells, and macrophages, leading to the production of pro-inflammatory cytokines like interleukin-6, which contributes to the systemic symptoms and elevated inflammatory markers characteristic of the disease. Management of PMR is based on prednisone 10-20 mg/day for grade 2 symptoms, as recommended in the recent guideline 1. In current practice, PMR is mainly treated by primary care physicians, whereas people with GCA are commonly referred to secondary/tertiary care specialists, and shared care between specialists and primary care physicians for both diseases is desirable, with regular evaluation of patients by an expert, particularly in case of difficult to treat PMR 1.
From the Research
Etiology of Polymyalgia Rheumatica (PMR)
The exact cause of polymyalgia rheumatica (PMR) is not fully understood, but it is believed to be related to a combination of genetic and environmental factors.
- PMR is an inflammatory condition that occurs in people over the age of 50, with the peak incidence at 70 to 75 years of age 2.
- It is characterized by proximal muscle pain, stiffness, and elevated inflammatory markers, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) 3, 2, 4.
- The diagnosis of PMR is clinical, consisting of at least two weeks of proximal muscle pain, constitutional symptoms, and elevated ESR or CRP 2.
- PMR is often associated with giant cell arteritis (GCA), a condition that involves inflammation of the blood vessels, particularly those in the head and neck 3, 4, 5, 6.
- The pathophysiology of PMR and GCA is not completely understood, but they may be related and often occur concurrently 4.
Risk Factors
Several risk factors have been identified for PMR, including:
- Age: PMR occurs in people over the age of 50, with the peak incidence at 70 to 75 years of age 2.
- Sex: PMR is more common in women than men 4.
- Genetics: There may be a genetic component to PMR, as it tends to run in families 3.
- Environmental factors: Some environmental factors, such as infections, may trigger the onset of PMR 6.
Triggers
Some potential triggers for PMR include:
- Infections: Some infections, such as those caused by viruses or bacteria, may trigger the onset of PMR 6.
- Autoimmune disorders: PMR may be associated with other autoimmune disorders, such as rheumatoid arthritis or lupus 3, 5.
- Hormonal changes: Hormonal changes, such as those that occur during menopause, may contribute to the development of PMR 4.