Diagnostic difficulties in polymyalgia rheumatica cases with normal erythrocyte sedimentation rate and C-reactive protein values

Naïve Inflammatory Proteome Profiles of Glucocorticoid Responsive Polymyalgia Rheumatica and Rheumatic Arthritis Patients-Links to Triggers and Proteomic Manifestations

Polymyalgia rheumatica (PMR) is an inflammatory disorder of unknown etiology, sharing symptoms with giant cell arthritis (GCA) and rheumatoid arthritis (RA). The pathogenic inflammatory roots are still not well understood, and there is a lack of extensive biomarker studies to explain the disease debut and post-acute phase. This study aimed to deeply analyze the serum proteome and inflammatory response of PMR patients before and after glucocorticoid treatment. We included treatment-naïve PMR patients, collecting samples before and after 3 months of treatment. For comparison, disease-modifying antirheumatic drug (DMARD)-naïve RA patients were included and matched to healthy controls (CTL). The serum proteome was examined using label-free quantitative mass spectrometry, while inflammation levels were assessed using multiplex inflammatory cytokine and cell-free DNA assays. The serum proteomes of the four groups comprised acute phase reactants, coagulation factors, complement proteins, immunoglobulins, and apolipoproteins. Serum amyloid A (SAA1) was significantly reduced by active PMR treatment. Cell-free DNA levels in PMR and RA groups were significantly higher than in healthy controls due to acute inflammation. Complement factors had minimal changes post-treatment. The individual serum proteome in PMR patients showed over 100 abundantly variable proteins, emphasizing the systemic impact of PMR disease debut and the effect of treatment. Interleukin (IL)-6 and interferon-gamma (IFN-γ) were significantly impacted by glucocorticoid treatment. Our study defines the PMR serum proteome during glucocorticoid treatment and highlights the role of SAA1, IL-6, and IFN-γ in treatment responses. An involvement of PGLYRP2 in acute PMR could indicate a response to bacterial infection, highlighting its role in the acute phase of the immune response. The results suggest that PMR may be an aberrant response to a bacterial infection with an exacerbated IL-6 and acute phase inflammatory response and molecular attempts to limit the inflammation.

Polymyalgia Rheumatica Post-SARS-CoV-2 Infection

There is growing evidence that infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can lead to dysregulation of the immune system and, consequently, the development of autoimmune phenomena. Here, we describe the case of a 75-year-old woman with rheumatic manifestations characterized by intense musculoskeletal pain and stiffness in the neck and shoulders, with sudden onset and with the inability to raise her arms. The patient was admitted with severe pain located in the neck and shoulders. Previously, she had oropharyngeal pain, severe fatigue, and fever; a real-time polymerase chain reaction test for COVID-19 was positive. Two weeks later, the patient presented localized musculoskeletal pain in the neck and shoulders. Relevant laboratory results included an erythrocyte sedimentation rate of 46 mm/hr and a negative rheumatoid factor test; ultrasound findings with bilateral subacromial-subdeltoid bursitis were observed. A diagnosis of polymyalgia rheumatica (PMR) was initially made according to the EULAR/ACR provisional classification criteria for PMR; however, due to C-reactive protein negativity, the diagnosis was established based on symptoms. Management was with prednisone at the dose of 25 mg/day for 4 weeks and progressive reduction until prednisone suspension. The patient showed complete recovery at 6 months of follow-up. In this case, COVID-19 was implicated in the development of autoimmune and inflammatory rheumatic manifestations. PMR is a rare rheumatic condition that should be included in the wide range of rheumatologic manifestations expressed post-SARS-CoV-2 infection.