Thrombocytosis as a prognostic factor in polymyalgia rheumatica: characteristics determined from cluster analysis

Mitochondrial-Mediated Platelet Activation in Polymyalgia Rheumatica

OBJECTIVE

Platelet activation is thought to participate in polymyalgia rheumatica (PMR) pathogenesis. Upon platelet activation, mitochondria are expelled into the extracellular space. However, whether extracellular mitochondria are present in patients with PMR and whether they can induce platelet activation is not known.

METHODS

To investigate this, we measured markers of platelet activation (thrombospondin-1 [TSP-1]), mitochondrial-derived N-formyl methionine peptide (fMET), and autoantibodies directed toward specific mitochondrial antigen mitofusin-1 (MFN1) by enzyme-linked immunosorbent assay in plasma of healthy controls (HCs, n = 30) and patients with PMR without giant cell arteritis (GCA) (n = 45) and patients with PMR with GCA (n = 9) before and after treatment with glucocorticoid therapy. Ultrapure mitochondria were opsonized with plasma from patients with PMR without GCA (n = 45) or HCs (n = 10) and were subsequently incubated with HC platelets. Platelet activation was assessed by P-selectin levels using flow cytometry.

RESULTS

Plasma levels of anti-MFN1 IgG were elevated in patients with PMR with and without GCA before glucocorticoid therapy when compared with HCs (P < 0.01 for both groups). Levels of anti-MFN1 IgG significantly reduced after treatment with glucocorticoids in both groups (P < 0.01). Levels of fMET were also significantly higher in patients with PMR with and without GCA before glucocorticoid therapy in comparison with HCs (P < 0.001 and P < 0.01, respectively). However, the levels of fMET only dropped significantly after therapy in patients with PMR without GCA (P < 0.001). Plasma levels of TSP-1 were elevated in patients with PMR with and without GCA before glucocorticoid therapy when compared to HC (P < 0.001 for both groups). After glucocorticoid therapy, plasma levels of TSP-1 decreased significantly only in patients with PMR without GCA (P = 0.023). Mitochondria opsonized with plasma from patients with PMR without GCA induced higher platelet activation regardless of treatment status as compared with plasma from HCs (P < 0.0001 and P < 0.01 for pretreatment and posttreatment).

CONCLUSION

Our results indicate increased platelet activation and the presence of mitochondrial antigens and antibodies in the circulation of patients with PMR. Blocking mitochondrial-mediated platelet activation may reduce inflammation in patients with PMR, with potential therapeutic implications.

High Relapse Rate in Patients with Polymyalgia Rheumatica despite the Combination of Immunosuppressants and Prednisolone: A Single Center Experience of 89 patients

Polymyalgia rheumatica (PMR) is an inflammatory disorder in the elderly and is characterized by pain in the shoulders and lower back. Previous studies from western countries have shown that relapse is frequent; however, there are only a few reports on the relapse rate in Japan. Here we examined the relapse rate, and sought to identify factors that predict recurrence in patients with PMR. Of 110 patients who fulfilled the Bird's criteria for PMR between May 2011 and June 2019, 21 patients were excluded, and the remaining 89 patients were followed up until July 2019. Relapse was defined when clinical symptoms were exacerbated and serum C-reactive protein level increased. The relapse-free survival curves were plotted using the Kaplan-Meier method, and log-rank test was used for statistical analysis. The mean age of the 89 patients (50 males and 39 females) was 71.8 years. The mean dose of initial prednisolone (PSL) was 11.8 mg/day. The 1-, 3-, and 5-year relapse-free survival rates were 81.6%, 58.0%, and 52.3% (N = 59, 21, and 7), respectively. In patients who experienced recurrence, the 1- and 3-year second relapse-free survival rates were 58.3% and 27.3% (N = 18 and 3), respectively. Immunosuppressants, such as methotrexate and tacrolimus, were added to PSL in 19 of 30 patients who experienced relapse at the discretion of the attending physicians; however, none of the immunosuppressants worked for preventing second relapses and had steroid-sparing effects. These results indicate that effective immunosuppressants are required to suppress relapse in the treatment of PMR.

Neutrophil to lymphocyte ratio predicts glucocorticoid resistance in polymyalgia rheumatica

AIM

Neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte ratio (PLR) correlate with disease activity in several rheumatic diseases; however, their utility in polymyalgia rheumatica (PMR) remains unclear. This study evaluated their relationship with disease activity and glucocorticoid resistance in PMR.

METHOD

Data for disease activity (PMR-AS) and full blood examination was obtained from a prospective observational cohort comprising newly diagnosed, steroid-naïve PMR patients treated with low-dose glucocorticoid therapy. Glucocorticoid resistance was defined as non-response to prednisolone 15 mg/d or initial response followed by flare (PMR-AS ≥ 9.35 or ∆ ≥6.6) upon weaning to 5 mg/d. Univariable Bayesian linear regression analysis of the relationship between PMR-AS (baseline and mean) and NLR and PLR was performed. Predictors of glucocorticoid resistance were identified using a multivariable outcome model, with variables derived from Bayesian model selection.

RESULTS

Of the 32 included patients, 16 (50%) fulfilled the primary outcome measure of glucocorticoid resistance. These participants were older, typically female, and had higher baseline C-reactive protein than their glucocorticoid-responsive counterparts. A statistically significant relationship was identified between PMR-AS and both NLR (odds ratio [OR] 28.1; 95% CI 1.6-54.7) and PLR (OR 40.6; 95% CI 10.1-71.4) at baseline, with PLR also found to correlate with disease activity during follow-up (OR 15.6; 95% CI 2.7-28.2). Baseline NLR proved a statistically significant predictor of glucocorticoid-resistant PMR (OR 14.01; 95% CI 1.49-278.06).

CONCLUSION

Baseline NLR can predict glucocorticoid resistance in newly diagnosed PMR patients. Both NLR and PLR may be reliable biomarkers of disease activity in PMR.