Polymyalgia rheumatica overview

# Overview
Polymyalgia rheumatica (PMR) is a chronic inflammatory disease that involves the articular and periarticular parts of the cervical region, shoulder girdle and pelvic girdle. PMR affects subjects over the age of 50 years and it is characterized by pain and stiffness in the neck, shoulders, upper arms, hip, and thighs. Although myalgia is one of the symptoms of PMR, there is no inflammation of the muscles; instead, PMR is a disease of the joint that causes synovitis. The diagnosis of PMR relies on the clinical findings and laboratory evidence of systemic inflammation. PMR is associated with giant cell arteritis. The cause of PMR is unknown but it has been suggested that both genetic and environmental factors are implicated. The mainstay of treatment of PMR is steroid therapy.

# Historical Perspective
Polymyalgia rheumatica was first described in 1888 by Bruce William as "senile rheumatic gout". The disease was referred to as "polymyalgia rheumatica" by Stuart Barber in 1957 in his article entitled "myalgic syndrome with constitutional effects; polymyalgia rheumatica".

# Classification
There is no established system for the classification of polymyalgia rheumatica.

# Pathophysiology
Polymyalgia rheumatica (PMR) is a chronic inflammatory disease of the articular and periarticular structures of the cervical region, shoulder girdle and hip girdle. The underlying pathophysiology of PMR remains unknown. It has been hypothesized that genetic and environmental factors are implicated, particularly due to the seasonal and geographical differences in the prevalence of this disease. It has also been hypothesized that PMR is associated with infections such as parainfluenza virus type 1, mycoplasma pneumoniae, chlamydia pneumoniae, and parvovirus B19. In addition, histological examinations of synovial biopsies of affected individuals reveal mild synovitis with predominance of CD4 T cells and macrophages. Although myalgia is a symptom of PMR, there is no inflammation of the muscles.The senescence of the immune systems as demonstrated by the loss of the CD28 on CD4+ T senescent cells may be responsible for aberrant immune responses in PMR. Adaptive immune alterations also occurs in PMR mainly represented by the activation of Th17 cells,  mainly driven by the increased IL-6 levels. An altered distribution and phenotype of B cells also occurs in PMR even in the absence of a clear autoimmune response.  Local activation  of myeloid and endothelial cells has been also demonstrated in the non-inflamed arteries and inflamed synovial tissues of PMR patients.

# Causes
There is no specific cause for polymyalgia rheumatica. However, there are possible theories about the causes which include inflammatory joint lining attack, viral infections, and genetic inheritance of HLA-DR4.

# Differentiating Polymyalgia Rheumatica from other Diseases
PMR must be differentiated from other conditions such as late onset rheumatoid arthritis, polymyositis, dermatomyositis, fibromyalgia, and remitting seronegative symmetrical synovitis with pitting edema.

# Epidemiology and Demographics
Polymyalgia rheumatica (PMR) affects mostly subjects who are more than 50 years of age. The prevalence of PMR is highest among subjects from Scandinavian countries and those from northern European origin.

# Risk Factors
Age, female sex, Scandinavia and northern Europe origin are risk factors for polymyalgia rheumatica. Other risk factors include smoking, sun exposure, infections, and nulliparity.

# Screening
There is insufficient evidence to recommend routine screening for polymyalgia rheumatica.

# Natural History, Complications and Prognosis
Polymyalgia rheumatica (PMR) affects the quality of life of the patients. The pain and stiffness in the proximal joints might lead to sleep disturbance as well as an inability to do regular daily activities such as getting dressed and getting out of a chair. The symptoms begin rapidly and last for weeks. Once the steroid treatment is initiated, the symptoms resolve rapidly within few days. In fact, the rapid resolution of symptoms with the steroid therapy reinforces the diagnosis of PMR. The steroid treatment can be associated with complications such as weight gain and bone fracture. Approximately 40 to 50% of subjects experience a relapse of the symptoms. PMR is associated with giant cell arteritis.

# Diagnosis

## Diagnostic Study of Choice
The diagnosis of polymyalgia rheumatica (PMR) is mostly clinical and it is supported with specific findings on laboratory tests and ultrasound of the affected joints. The European League Against Rheumatism/American College of Rheumatology collaborative initiative developed a provisional classification criteria for PMR. The following criteria are required for the diagnosis of PMR: age more than 50 years, bilateral shoulder pain, and elevated C-reactive protein (CRP) and/or erythrocyte sedimentation rate (ESR).

## History and Symptoms
Polymyalgia rheumatica (PMR) is typically characterized by symmetrical pain and morning stiffness in the proximal joints and limbs, including the neck, the shoulder girdle, the pelvic girdle, the lower back, and the thighs. In some patients, there is involvement of the distal parts of the body such as peripheral synovitis or arthritis. Constitutional symptoms can also be present, and they include fever, fatigue, loss of appetite, and weight loss. There is an association between PMR and giant cell arteritis which can present with one or more of the following symptoms that include headaches, scalp tenderness, jaw claudication, fever, or distorted vision.

## Physical Examination
Physical examination of patients with polymyalgia rheumatica reveals limitation of the active and passive range of motion of the affected joint. There is no true muscle weakness. There are no changes in the joints. Ophthalmoscopic exams in patients with polymyalgia rheumatica associated with giant cell arteritis might be abnormal.

## Laboratory Findings
Polymyalgia rheumatica (PMR) is a clinical diagnosis that is supported by laboratory tests. Elevation of C-reactive protein (CRP) and/or erythrocyte sedimentation rate (ESR) is essential for the diagnosis of PMR.

## Electrocardiogram
There are no EKG findings associated with polymyalgia rheumatica.

## X Ray
There are no x ray findings associated with polymyalgia rheumatica.

## Echocardiography and Ultrasound
There are no echocardiography findings associated with polymyalgia rheumatica. Ultrasound exam is important for the diagnosis of polymyalgia rheumatica (PMR). It can reveal evidence of bursitis, synovitis or tenosynovitis in the affected areas.

## CT Scan
There are no CT findings associated with polymyalgia rheumatica.

## MRI
MRI is used for the assessment of bursitis, synovitis, and tenosynovitis among patients with polymyalgia rheumatica (PMR). MRI is more sensitive than ultrasonography for the evaluation of iliopsoas bursitis and hip synovitis. A study has demonstrated that MRI of the shoulders facilitates the proper diagnosis in patients with the typical proximal symptoms of PMR with normal ESR values.

## Other Imaging Findings
There are no other imaging findings associated with polymyalgia rheumatica.

## Other Diagnostic Studies
A muscle biopsy might be performed to differentiate polymyalgia rheumatica (PMR) from other diseases. In addition, temporal artery biopsy is required when a subject with PMR have symptoms suggestive of giant cell arteritis.

# Treatment

## Medical Therapy
The mainstay of treatment of polymyalgia rheumatica (PMR) is low dose glucocorticoids, typically prednisone or prednisolone. The starting dose of the glucocorticoid treatment is 12.5-15 mg daily for 2 to 4 weeks after which the treatment should be slowly tapered. The average duration of the treatment with glucocorticoids is 1 to 2 years; nevertheless, longer corticosteroids regimens might be necessary among patients who experience relapse of the symptoms. Prophylaxis for osteoporosis with calcium and vitamin D should be started with the steroid therapy.

## Surgery
Surgical intervention is not recommended for the management of polymyalgia rheumatica.

## Primary Prevention
There are no established measures for the primary prevention of polymyalgia rheumatica.

## Secondary Prevention
There are no established measures for the secondary prevention of polymyalgia rheumatica.