Despite considerable research, the cause of PMR remains obscure. Since nearly all patients are aged over 50 years, there is clearly some relationship to age. However, the relevance of this is unclear. There is an increased frequency of the genetic allele
HLA-DR4 in patients when compared with controls (see hla). This may indicate that patients have a genetically determined way of responding to antigens that predisposes them to getting the disease. There are certainly a number of families where two or more members have developed PMR. However, there are also reports of husbands and wives developing PMR that would support exposure to the same antigen rather than hereditary factors as a cause.
The walls of affected arteries in temporal arteri-tis (and sometimes in uncomplicated PMR) are affected in patches. A chronic immune attack which classically leads to organized clumps of immune cells arranged in what is termed a granuloma. only arteries with elastic layers in their walls are attacked, and the attack seems to be centered on or close to this elastic layer. The smaller arteries lose the elastic layer, so mostly large or medium-sized arteries are affected. There have been a number of postulated antigens that might initiate the immune response, but none have stood up to further investigation.
Typically an older individual in good health develops a low-grade fever and loses some weight. Transient aches and pains may be present for weeks or months. The pain and stiffness settles in a shoulder and then moves to both the hip and the shoulder region within a few weeks. Less commonly a patient wakes up one morning unable to get out of bed because of the pain and stiffness. Lethargy and depression are common. Severe stiffness on rising in the morning is characteristic, and it several hours may pass before the patient is able to move about reasonably normally. This characteristic stiffness often returns when the individual sits down to rest during the day. pain and waking at night are common. Although movement makes the pain worse, the pain usually described as being in the muscles rather than the joints. Muscle strength is normal, although pain may make it difficult for the patient to be sure of this.
Some patients do have an associated arthritis, usually affecting the knees, wrists, or sternoclavic-ular (between the collarbone and breastbone) joints. Between 10 and 20 percent of patients with pMR develop temporal arteritis. on the other hand, between 20 and 40 percent of patients with temporal arteritis have symptoms of PMR. Temporal arteritis is discussed separately.
No diagnostic test is available for PMR. Biopsy of a temporal artery can confirm temporal arteritis if this is present and may occasionally be positive in uncomplicated PMR. However, in the absence of a diagnostic test it is important to exclude other conditions that can present in a similar way. This is particularly important when the onset is atypical in some way. The ESR is almost always raised. Although polymyalgia with a normal ESR is frequently discussed, this is very rare. Typically the ESR will be raised to between 50 and 100 mm per hour. Other markers of inflammation such as C-reactive protein will also be raised, and a rise in alpha globulins is common but nonspecific. Many studies have shown a selective reduction in CD8+ T cells in patients with pMR that returns to normal after about one year of treatment. Researchers have hoped that this might provide a more specific test for pMR, but confirmation is awaited. The enzymes released by an inflamed or damaged liver (especially alkaline phosphatase) are frequently mildly raised, and liver biopsies have shown mild inflammatory changes in pMR (see Appendix ii for description of tests). The important characteristics in making the diagnosis are some combination of the following: a Caucasian patient aged over 50 years with persistent (more than a month) pain in the shoulders and pelvic girdle, marked morning stiffness, no true muscle weakness, an ESR over 40 mm per hour, and excellent relief with a small dose of PREDNISONE.
The fewer of these characteristics that are present, the less typical the illness is and the more likely it is to be another illness presenting like PMR. rheumatoid arthritis starting for the first time in an older individual is well known to mimic PMR. Multiple myeloma and lung cancer are the two malignancies most likely to produce this type of syndrome, but a number of other malignancies that have spread to bone can also do this. Osteoarthritis (OA) of the neck is very common. When combined with the lethargy, loss of appetite, and raised ESR caused by an unrecognized low-grade infection, oA may lead to an erroneous diagnosis of PMR. Leukemias and lymphomas may occasionally cause confusion as can myopathies, myositis, and hypothyroidism.
Treatment corticosteroids are almost always required. With mild disease it is possible to try NSAIDs first. However, these drugs have greatly increased toxicity in the elderly. It is therefore often safer and more effective to use corticosteroids, usually prednisone. The majority of patients will experience marked-to-miraculous relief with 15 mg of prednisone daily. occasionally patients will need higher doses, but this should prompt a careful consideration of whether the diagnosis is correct. The dose may be reduced to 10 mg per day over two months and then very gradually reduced as symptoms and the ESR allow. Too rapid a reduction results in more relapses, and these patients end up taking more prednisone than they would have with a more gradual reduction. Treatment is usually required for between two and five years, when it may be stopped without any recurrence of the PMR. A very small number of patients continue to take a small dose of prednisone for many years. If it is not possible to reduce the pred-nisone without a recurrence of symptoms or the cor-ticosteroid side effects are too great, another medication is usually added. This is usually azathio-prine, but methotrexate has also been used.
once the initial inflammation is controlled, the patient usually feels very much better. The most difficult aspect of treatment is in limiting the corticos-teroid side effects. The risk of osteoporosis should be evaluated. Most patients will benefit from preventive treatment, at least for the duration of the prednisone therapy. corticosteroids and inflammation may promote atherosclerosis. Since many PMR patients are at an age where they are at risk of cardiovascular events, they should take an antiplatelet agent such as low-dose aspirin. This has not been submitted to controlled trial and is unlikely to be because of the cost of such a trial. Protection from bruising and limiting weight gain are also important in long-term corticosteroid therapy.
Although there is some variation between different studies, at least 50 percent of patients should be able to stop treatment after two years and the vast majority by four to five years. Between 20 and 50 percent of patients will suffer significant adverse effects from the long-term prednisone therapy. The risk of adverse effects is related to higher initial doses, total dose taken, and longer duration of treatment.
polymyositis See dermatomyositis and polymyositis.
pregnancy Patients with rheumatic diseases face three major questions during pregnancy.
1. What is the effect of drugs used to treat rheumatic disease on pregnancy?
2. How can pregnancy affect rheumatic illness?
3. How can rheumatic illness affect the pregnancy?
These questions are difficult to answer because each individual's situation is different and there is not much information available from clinical trials. The treatment of rheumatic disease in pregnancy is complicated and best performed by a team of physicians bringing together obstetric and rheumatology expertise.
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