Polymyalgia Rheumatica and Seronegative Elderly-Onset Rheumatoid Arthritis: Two Different Diseases with Many Similarities

Abstract

Polymyalgia rheumatica (PMR) and seronegative elderly-onset rheumatoid arthritis (SEORA) are two of the most frequent inflammatory rheumatologic diseases in elderly patients. At first presentation, there are many similarities between PMR and SEORA, that may lead to a real diagnostic conundrum. The most relevant similarities and differences between PMR and SEORA are discussed in this review. In addition to the acute involvement of the shoulder joints, important features characterising both diseases are morning stiffness longer than 45 minutes, raised erythrocyte sedimentation rate, and a good response to low doses of prednisone. Some findings (such as erosive arthritis or symmetrical involvement of metacarpophalangeal and/or proximal interphalangeal joints) can help to make the diagnosis of SEORA, whereas shoulder and hip ultrasonography and 18-FDG PET/CT seem to be less specific. However, in several patients only long-term follow-ups confirm the initial diagnosis. A definite diagnosis of PMR or SEORA has significant therapeutic implications, since patients with PMR should be treated with long-term glucocorticoids, and sometimes throughout life, which predisposes the patients to serious side effects. On the contrary, in patients with SEORA, short-term treatment with glucocorticoids should be considered when initiating or changing disease modifying antirheumatic drugs, followed by rapid tapering.

Differentiating between Seronegative Elderly-Onset Rheumatoid Arthritis and Polymyalgia Rheumatica: A Qualitative Synthesis of Narrative Reviews

“…The presence of joint pain does not rule out the possibility of PMR. Accordingly, another review revealed not only the similarity between the two at the initial presentation but also the continuity from PMR to seronegative EORA, which may hinder diagnosis [21]. Furthermore, shoulder pain and arthritis can appear in both diseases; therefore, shoulder symptoms are not used for their differentiation.…”

“…A quarter of PMR patients may also have asymmetric non-erosive polyarthritis, which highlights the need for a good differential diagnosis [19]. Another review reported that >20% of patients with PMR were later diagnosed with rheumatoid arthritis, which lent to the theory that PMR and EORA are components of a single disease process [21]. Some types of seronegative EORA involve PMR presentation; therefore, the differentiation from PMR can be challenging because this disease is a part of the EORA clinical disease picture.…”

“…Arthritis of various peripheral joints suggests seronegative EORA. One review suggested, "An erosive arthritis or the symmetrical involvement of metacarpophalangeal and/or proximal interphalangeal joints can help to diagnose seronegative EORA" [21]. Another reported, "The presence of metacarpophalangeal (MCP)/proximal interphalangeal (PIP) joint arthritis with proximal limb joint involvement is considered a predictive factor for seronegative EORA" [19].…”

Why would immuno- and endocrino-senescence, age-related changes in the gut microbiota, and susceptibility to infection favour polymyalgia rheumatica over seronegative elderly-onset rheumatoid arthritis?

“…The relationship between PMR and SE-ORA has been variously interpreted over the years. Nowadays, data allow PMR and SEORA to be classified as nosographically distinct (3)(4)(5). Specifically, erosive arthritis and symmetrical involvement of metacarpophalangeal joints are absent in patients with PMR (6).…”

“…On the other hand, the fact that an initial diagnosis of PMR may change to SEORA and vice versa during follow-up, and that SEORA patients may have PMR features at onset (so-called "SEORA with PMR-like onset") emphasises that PMR and SEORA have many similarities so that it can be difficult to differentiate these diseases each from other (9,10). We recognise that a few studies involved a head-to-head comparison between SEORA and PMR pathogenesis (2,4,8,9). Immunosenescence/inflammaging, the so-called "endocrine-senescence", and age-related changes in gut microbiota seem to be common in older adults.…”