Polymyalgia rheumatica

Abstract

This chapter reviews advances in pathogenesis; European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) classification criteria with clinical, laboratory, and ultrasound criteria for classification as polymyalgia rheumatica (PMR); the heterogeneity and overlap between PMR, inflammatory arthritis, and large-vessel vasculitis as illustrated by representative cases; recent guidelines on early and correct recognition, investigations, and management of PMR; the scope of disease-modifying agents; socio-economic impact, outcomes, and patient experience in PMR. It also discusses areas for future research including clinical trials with biological agents and newer steroid formulations, standardized outcome assessments, and the search for better biomarkers in PMR. PMR is one of the common inflammatory rheumatic diseases of older people and represents a frequent indication for long-term glucocorticoid (GC) therapy. It is characterized by abrupt-onset pain and stiffness of the shoulder and pelvic girdle muscles. Its management is subject to wide variations of clinical practice and it is managed in primary or secondary care by general practitioners (GPs), rheumatologists, and non-rheumatologists. The evaluation of PMR can be challenging, as many clinical and laboratory features may also be present in other conditions, including other rheumatological diseases, infection, and neoplasia. PMR is usually diagnosed in the primary care setting, but standard clinical investigations and referral pathways for suspected PMR are unclear. The response to standardized therapy is heterogeneous, and a significant proportion of patients do not respond completely. There is also an overlap with inflammatory arthritis and large-vessel vasculitis for which adjuvant disease-modifying medications are often used. Prolonged corticosteroid therapy is associated with a variety of side effects, especially when high-dose glucocorticoid therapy is employed. Giant cell arteritis (GCA) is also often linked to PMR. It is a vasculitis of large- and medium-sized vessels causing critical ischaemia. GCA is a medical emergency because of the high incidence of neuro-ophthalmic complications. Both conditions are associated with a systemic inflammatory response and constitutional symptoms. The pathogenesis is unclear. The initiating step may be the recognition of an infectious agent by aberrantly activated dendritic cells. The key cell types involved are CD4+ T cells and macrophages giving rise to key cytokines such as interferon-γ‎ (implicated in granuloma formation), PDGF (intimal hyperplasia), and interleukin (IL)-6 (key to the systemic response). The pathogenesis of PMR may be similar to that of GCA, although PMR exhibits less clinical vascular involvement. The mainstay of therapy is corticosteroids, and disease-modifying therapy is currently indicated in relapsing disease.