Clinical features of the patients stratified according to the pattern of presentation
| Polyarthritis (n=18) | Oligoarthritis (n=21) | PMR-like (n=27) | P value | |
| Age (years) | 54±16 | 64±15 | 67±10 | 0.006 |
| Female gender, n (%) | 10 (55.6) | 16 (76.2) | 17 (63.0) | 0.696 |
| Past COVID-19, n (%) | 2 (11.1) | 1 (4.8) | 0 (0.0) | 0.211 |
| Specific vaccine administered | ||||
| BNT162b2, n (%) | 9 (50.0) | 12 (57.1) | 18 (66.7) | 0.363 |
| mRNA-1273, n (%) | 0 (0.0) | 1 (4.8) | 2 (7.4) | 0.535 |
| AZD1222, n (%) | 9 (50.0) | 7 (33.3) | 7 (25.9) | 0.197 |
| Ad26.COV2.S, n (%) | 0 (0.0) | 1 (4.8) | 0 (0.0) | 0.295 |
| Vaccine-related adverse events | ||||
| None, n (%) | 3 (16.7) | 9 (42.9) | 11 (40.7) | 0.195 |
| Pain at the injection site, n (%) | 12 (66.7) | 10 (47.6) | 13 (48.1) | 0.440 |
| Fever, n (%) | 5 (27.8) | 1 (4.8) | 3 (11.1) | 0.112 |
| Headache, n (%) | 2 (11.1) | 2 (9.5) | 2 (7.4) | 0.869 |
| Fatigue, n (%) | 6 (33.3) | 3 (14.3) | 1 (3.7) | 0.023 |
| Rheumatic manifestation onset after first dose, n (%) | 11 (61.1) | 7 (33.3) | 12 (44.4) | 0.322 |
| Delay between vaccine administration and rheumatic manifestation onset (days) | 12±9 | 11±7 | 13±7 | 0.450 |
| Rheumatic manifestations | ||||
| Symmetrical involvement, n (%) | 15 (83.3) | 9 (42.9) | 24 (88.9) | 0.001 |
| Involvement of small joints, n (%) | 11 (61.1) | 4 (19.0) | 2 (7.4) | <0.001 |
| Tenosynovitis, n (%) | 7 (38.9) | 4 (19.0) | 2 (7.4) | 0.029 |
| Enthesitis, n (%) | 0 (0.0) | 3 (14.3) | 0 (0.0) | 0.023 |
| Bursitis, n (%) | 1 (5.6) | 1 (4.8) | 0 (0.0) | 0.456 |
| Inflammatory back pain with MRI evidence of sacroiliitis or spondylitis, n (%) | 1 (5.6) | 1 (4.8) | 0 (0.0) | 0.456 |
| Fatigue, n (%) | 4 (22.2) | 3 (14.3) | 8 (29.6) | 0.613 |
| Laboratory features | ||||
| ESR (mm/hour) | 51±34 | 36±25 | 45±28 | 0.108 |
| CRP (mg/dL) | 2.13 (1.25–5.20) | 1.90 (0.50–3.61) | 2.13 (1.25–5.20) | 0.121 |
| RF positive, n (%)* | 1 (6.3) | 0 (0.0) | 0 (0.0) | 0.255 |
| ACPA positive, n (%)* | 1 (6.3) | 0 (0.0) | 0 (0.0) | 0.255 |
| RF and ACPA positive, n (%)* | 1 (6.3) | 0 (0.0) | 0 (0.0) | 0.255 |
| ANA positive, n (%)† | 2 (15.4) | 3 (17.6) | 0 (0.0) | 0.061 |
| Treatment | ||||
| NSAIDs, n (%) | 6 (33.3) | 11 (52.4) | 9 (33.3) | 0.507 |
| Paracetamol or opioids, n (%) | 5 (27.8) | 3 (14.3) | 6 (22.2) | 0.669 |
| Glucocorticoids, n (%) | 9 (50.0) | 13 (61.9) | 21 (77.8) | 0.113 |
| Methotrexate, n (%) | 4 (22.2) | 5 (23.8) | 3 (11.1) | 0.490 |
| Sulfasalazine, n (%) | 1 (5.6) | 0 (0.0) | 0 (0.0) | 0.523 |
| Follow-up duration (weeks) | 6 (2–8) | 4 (3–8) | 2 (1–5) | 0.209 |
| Outcome | ||||
| Active disease, n (%) | 12 (66.7) | 9 (42.9) | 6 (22.2) | 0.007 |
| Remission, n (%) | 6 (33.3) | 10 (47.6) | 20 (74.1) | 0.014 |
| N/A, n (%) | 0 (0.0) | 2 (9.5) | 1 (3.7) | 0.296 |
Data are expressed as mean±SD or median (25th–75th percentiles), as appropriate. P values refer to one-way analysis of variance or Kruskal-Wallis H test for continuous or categorical variables, respectively (in bold p values < 0.05).
*Information for RF/ACPA status available for 56 patients.
†Information for ANA status available for 48 patients.
ACPA, anticitrullinated protein antibody; ANA, antinuclear antibody; CRP, C reactive protein; ESR, erythrocyte sedimentation rate; N/A, not available; NSAID, non-steroidal anti-inflammatory drug; PMR, polymyalgia rheumatica; RF, rheumatoid factor.