NMR-based clinical metabolomics revealed distinctive serum metabolic profiles in patients with spondyloarthritis.

Spondyloarthritis (SpA) is a common rheumatic disorder of the young, marred by delay in diagnosis, and paucity of biomarkers of disease activity. The present study aimed to explore the potential of serum metabolic profiling of patients with SpA to identify biomarker for the diagnosis and assessment of disease activity. The serum metabolic profiles of 81 patients with SpA were compared with that of 86 healthy controls (HCs) using nuclear magnetic resonance (NMR)-based metabolomics approach. Seventeen patients were followed up after 3 months of standard treatment, and paired sera were analyzed for effects of therapy. Comparisons were done using the multivariate partial least squares discriminant analysis (PLS-DA), and the discriminatory metabolic entities were identified based on variable importance in projection (VIP) statistics and further evaluated for statistical significance (p value < 0.05). We found that the serum metabolic profiles differed significantly in SpA as compared with HCs. Compared with HC, the SpA patients were characterized by increased serum levels of amino acids, acetate, choline, N-acetyl glycoproteins, Nα-acetyl lysine, creatine/creatinine, and so forth and decreased levels of low-/very low-density lipoproteins and polyunsaturated lipids. PLS-DA analysis also revealed metabolic differences between axial and peripheral SpA patients. Further metabolite profiles were found to differ with disease activity and treatment in responding patients. The results presented in this study demonstrate the potential of serum metabolic profiling of axial SpA as a useful tool for diagnosis, prediction of peripheral disease, assessment of disease activity, and treatment response.

Nuclear magnetic resonance-based metabolomics reveals similar metabolomics profiles in undifferentiated peripheral spondyloarthritis and reactive arthritis.

INTRODUCTION: After exclusion of reactive, psoriatic and enteritis-associated arthritis, a group of "undifferentiated" peripheral spondyloarthritis (pSpA) remains. This group shares genetics, T-cell repertoire, and cytokines with reactive arthritis (ReA). ReA is preceded by gut or urogenital infection. Otherwise the two may be similar. We know little of the metabolic pathways driving undifferentiated pSpA or ReA. Nuclear magnetic resonance (NMR)-based metabolomics presents a hypothesis-free approach to study and compare metabolic pathways driving undifferentiated pSpA and ReA. METHODS: Serum and synovial fluid metabolomes of 19 ReA and 13 undifferentiated pSpA, and serum metabolome of 18 controls were profiled using 1 H-based NMR. Partial least square-discriminant analysis (PLS-DA) identified metabolites different in patients as compared to controls. Multivariate analysis confirmed these. Altered metabolic pathways were identified using metabolites set enrichment analysis (MSEA). The serum and synovial fluid metabolomes of ReA and undifferentiated pSpA were compared. RESULTS: Ten serum metabolites of ReA/undifferentiated pSpA were different from those of controls. Six metabolites were different between serum and synovial fluid of these patients. MSEA identified five pathways different between patients and controls, and five pathways different between serum and synovial fluid of patients. PLS-DA showed no difference between the metabolomes of serum or of synovial fluid between ReA and undifferentiated pSpA. DISCUSSION: Identified metabolic pathways may be explored further to understand the pathogenesis and to target therapeutics. The similar immuno-metabolic pathways suggest similar pathogenesis of ReA and undifferentiated pSpA. Thus, they should be studied as a single disease entity.

Strongly positive anti-CCP antibodies in patients with sacroiliitis or reactive arthritis post-E. coli infection: A mini case-series based review.

We report here on four cases of patients with strongly positive anti-citrullinated cyclic peptides (anti-CCP) antibodies and clinical features of seronegative spondyloarthritis (SpA) and reactive arthritis. The four patients had various clinical presentations: one had an initial diagnosis of seropositive rheumatoid arthritis (RA) with involvement of the sacroiliac joints (similar to previous reports of the association of two diseases); one had a clinical picture of reactive arthritis following an episode of an Escherichia coli positive urinary tract infection; and two had asymmetrical sacroiliitis (SII), but no evidence of peripheral joint involvement (never reported before). In all cases, high titers of anti-CCP antibodies were found. We present a comparison of the clinical manifestations, radiographic features and treatment regimens of these cases. Our report supports previous literature data of possible overlap existing between RA and SpA, but also presents for the first time the association of high titers of anti-CCP antibodies with SII and reactive arthritis in patients with no peripheral small joint involvement.

HLA-B27 Correlates with the Intracellular Elimination, Replication, and Trafficking of Salmonella Enteritidis Collected from Reactive Arthritis Patients.

BACKGROUND The aim of this study was to explore the correlation between HLA-B27 and the intracellular elimination, replication, and trafficking of Salmonella enteritidis (S. enteritidis) collected from patients with reactive arthritis. MATERIAL AND METHODS Confocal microscopy, flow cytometry, and sandwich enzyme-linked immunosorbent assay (ELISA) were employed in this study to evaluate the localization of proteins of interest, to assess the intracellular trafficking of S. enteritidis, and to measure the production of cytokines of interest. RESULTS HLA-B27 was negatively associated with intracellular S. enteritidis elimination in healthy human monocytes/macrophages. In S. enteritidis infected monocytes/macrophages, HLA-27B was also negatively correlated with bacteria elimination but positively related to bacteria replication. S. enteritidis did not co-localize with NRAMP1 and LAMP1/2 in HLA-B27 cells. S. enteritidis did not co-exist with transferrin or dextran within HLA-B27 and A2 cells. CONCLUSIONS HLA-B27 is closely associated with the intracellular elimination and replication of S. enteritidis. Replicated bacteria in HLA-B27 monocytic cells were located within unique vacuoles rather than disturbing host endocytosis.

[Reactive arthritis: inflammation or true infection?]. / Arthrites réactionnelles: réactions inflammatoires ou vraie infection?

Reactive arthritis has been classically defined as an aseptic arthritis induced by a bacterial infection in another organ. If the classical form of reactive arthritis is in fact a spondyloarthritis triggered by a urogenital or intestinal bacterial infection, it is not necessarily sterile, and in some cases it may be worthwhile to treat a chronic infection with long-term antibiotherapy. In a broader definition, the concept of reactive arthritis is widened to other post-infectious rheumatism, such as post-streptococcal arthritis or post-viral arthritis.

Seronegative reactive spondyloarthritis and the skin.

Spondyloarthritidies represent a group of conditions affecting the axial and peripheral muscoloskeletal apparatus and are often associated with psoriasis, infections, and inflammatory bowel diseases. Other diseases included in this category are psoriatic arthritis, ankylosing spondylitis, and enteropathic arthritis. Reactive arthritis is an elusive spondyloarthritis, commonly occurring 1 to 3 weeks after a digestive or a genitourinary tract infection, in which microorganisms do not infect the joint directly. Reactive arthritis is classically characterized by large-joint arthritis, urethritis in men and cervicitis in women, and eye inflammation (usually conjunctivitis or uveitis) but encompasses numerous other symptoms and signs, including manifestations of dermatologic interest such as keratoderma blenorrhagicum and circinate balanitis. The diagnosis of reactive arthritis is clinical, and the infectious agent cannot always be identified due to disease latency after the infection. Most cases are self-limiting, but reactive arthritis may become chronic in 30% of cases. Treatment options include anti-inflammatory drugs, steroids, and sulfasalazine; biologic agents, such as tumor necrosis factor α (TNF-α) blockers, have been recently used, but there are only a few randomized clinical trials on the treatment of reactive arthritis. The effectiveness of antimicrobials needs further evaluation.

Lone aortic insufficiency and conduction disease: a marker of reactive arthritis.

A 48-year-old male with history of chronic arthritis and uveitis presented with 1 year of progressively reduced exercise capacity and nonexertional chest pain. Physical examination was consistent with severe aortic insufficiency. An electrocardiogram demonstrated sinus rhythm with first degree atrioventricular block. Transthoracic and transesophageal echocardiography demonstrated severe lone central aortic insufficiency of a trileaflet valve due to leaflet thickening, retraction of leaflet margins and mild aortic root dilation in the setting of left ventricular dilatation. In addition, computed tomographic angiography revealed a small focal aneurysm of the distal transverse arch. He was found to be positive for the immunogenetic marker HLA-B27. The patient subsequently underwent uncomplicated mechanical aortic valve replacement. The diagnosis of HLA-B27 associated cardiac disease should be entertained in any individual with lone aortic insufficiency, especially if accompanied by conduction disease.

[Frequency of antibodies to the recombinant protein P39 of C. jejuni in patients with gastrointestinal disorders and reactive arthritis in Poland]. / Czestosc wystepowania przeciwcial dla rekombinowanego bialka P39 paleczek C. jejuni u wybranych osób z zaburzeniami zoladkowo-jelitowymi oraz z reaktywnym zapaleniem stawów w Polsce.

INTRODUCTION: Campylobacterjejuni is has been found to be the leading cause of bacterial gastroenteritis worldwide. Clinical manifestation on enterocolitis caused by C. jejuni are diarrhea, fever, abdominal pain and in some patients, fecal blood. After C. jejuni infection, squeals may occur such as reactive arthritis. The aim of the study was to investigate the frequency of antibodies to the recombinant protein P39 sticks C. jejuni in patients with gastrointestinal disorders and reactive arthritis in Poland. MATERIAL AND METHODS: Serum samples collected from 46 patients with bacteriology confir- med infection caused by Campylobacter jejuni, 472 sera from patients with gastrointestinal disorders, 97 serum samples obtained from patients with reactive arthritis and 84 sera from healthy adults and children. Sera were screened for anti-P39 C. jejuni recombinant protein IgA, IgG andIgM antibodies by using the home-made ELISA. Protein P39 C. jejuni was expressing in E. coli BL21 (DE3) using the pET-30 Ek/LIC expression vector. Purification was accomplished by immobilized metal (Ni2+) affinity column chromatography (His Bind Resign, Novagen). RESULTS: SDS-PAGE and Coomassie brilliant blue staining confirmed a high purity of the recombinant P39 protein preparation with an expected molecular mass of 39 kDa. The results of ELISA with the P39 recombinant protein revealed that IgA antibodies in diagnostically significant level (x + 2SD) were found in 18.8%, IgM in 14.8% and IgG in 7.8% of sera obtained from patients with of gastrointestinal disorders. On the other hand, antibodies to recombinant P39 protein in sera obtained from patients with reactive arthritis were found in more than twice the percentage than in patients with gastrointestinal disorders (IgA in 34.0%, IgG in 26.8% and IgM in 19.6%). CONCLUSIONS: In conclusion, based on the data obtained, C. jejuni may be important factor in triggering the gastrointestinal disorder and reactive arthritis in humans in Poland.

Normal inflammasome activation and low production of IL-23 by monocyte-derived macrophages from subjects with a history of reactive arthritis.

OBJECTIVES: The pathogenesis of reactive arthritis (ReA) is incompletely understood but may involve aberration(s) in the host's innate immune response towards infecting microbes. We therefore studied the production of interleukin (IL)-1ß, a marker of inflammasome activation, and of IL-6, IL-12, IL-23, and tumour necrosis factor (TNF)-α, promoters of T-cell differentiation, by peripheral blood mononuclear cells (PBMNs) and monocyte-derived macrophages from healthy subjects with a history of ReA. METHOD: The study included 10 human leucocyte antigen (HLA)-B27-positive healthy subjects with previous ReA triggered by Yersinia enterocolitica O:3 infection and 20 healthy reference subjects, of whom 10 were HLA-B27 positive. PBMNs and macrophages were cultured for 18 h with bacterial lipopolysaccharide (LPS), muramyl dipeptide (MDP), Yersinia, or their appropriate combinations. PBMNs were also stimulated with monosodium urate (MSU) crystals. Cytokine levels were measured using an enzyme-linked immunosorbent assay (ELISA) and the Luminex system. RESULTS: IL-1ß secretion was similar from cells of the ReA group and from the HLA-B27-positive and -negative reference groups. TNF-α production from macrophages upon co-stimulation of LPS and MDP increased in the order ReA group < HLA-B27-positive reference group < HLA-B27-negative reference group (p for a trend = 0.027). Similarly, Yersinia-induced TNF-α and IL-23 production increased in the same order (p for trend for TNF-α = 0.036; p for trend for IL-23 = 0.026). CONCLUSIONS: PBMNs and macrophages from healthy subjects with previous ReA show normal inflammasome activation and low TNF-α and IL-23 production. This low cytokine production may impair bacterial elimination and thereby contribute to the triggering of ReA.

[The criteria of differentiated diagnostics of early arthritis on the basis of analysis of serum hyaluronidase and deoxyribonuclease activity].

The study analyzed serum hyaluronidase and deoxyribonuclease activity in patients with early arthritis--early rheumatoid arthritis and acute reactive arthritis. The criteria of their differential diagnostics were developed on the basis of data obtained. The genuine methods were applied to analyze hyaluronidase and deoxyribonuclease activity of blood serum based on formation of clot of etacridine acetate (rivanol) with hyaluronic acid and DNA inversely proportionally to their polymerization under the impact of enzymes. The increased serum hyaluronidase and deoxyribonuclease activity was established in patients with early arthritis as compared with control group (p < 0.001). The prevalence of mentioned types of activity under early rheumatoid arthritis as compared with acute reactive arthritis was detected too. The rests for differentiate diagnostics of early rheumatoid arthritis and acute reactive arthritis were developed conformed to criteria of the most useful diagnostic tests in rheumatology.

Serum COMP-C3b complexes in rheumatic diseases and relation to anti-TNF-α treatment.

INTRODUCTION: Cartilage oligomeric matrix protein (COMP) is found at elevated concentrations in sera of patients with joint diseases such as rheumatoid arthritis (RA) and osteoarthritis (OA). We recently showed that COMP activates complement via the alternative pathway and that COMP-C3b complexes are present in sera of RA patients, but not in healthy controls. We now set out to elaborate on the information provided by this marker in a variety of diseases and larger patient cohorts. METHODS: COMP-C3b levels in sera were measured by using an enzyme-linked immunosorbent assay (ELISA) capturing COMP and detecting C3b. Serum COMP was measured by using ELISA. RESULTS: COMP-C3b levels were significantly elevated in patients with RA as well as in systemic lupus erythematosus (SLE), compared with healthy controls. SLE patients with arthritis had significantly higher COMP-C3b levels than did those without. COMP-C3b was furthermore elevated in patients with ankylosing spondylitis (AS), psoriatic arthritis (PsA), reactive arthritis, systemic sclerosis, and OA. COMP-C3b did not correlate with COMP in any of the patient groups. COMP-C3b correlated with disease activity in RA, but not in other diseases. COMP-C3b levels in RA patients decreased on treatment with tumor necrosis factor (TNF)-α inhibitors, whereas the levels increased in patients with AS or PsA. The changes of COMP-C3b did not parallel the changes of C-reactive protein (CRP). CONCLUSIONS: COMP-C3b levels are elevated in several rheumatologic diseases and correlate with inflammatory measures in RA. COMP-C3b levels in RA decrease during TNF-α inhibition differently from those of CRP, suggesting that formation of COMP-C3b relates to disease features not reflected by general inflammation measures.

Detection of bacterial DNA in peripheral blood mononuclear cells of patients with reactive arthritis.

Reactive arthritis (ReA) is an infection-induced systemic illness characterized by an aseptic inflammatory joint involvement and occurring in genetically predisposed patients with a bacterial infection localized in a distant organ or system. We evaluated the possible role of bacterial infection in the etiology of reactive arthritis by testing peripheral blood monocytes (PBMCs) for the presence of prokaryotic 16S ribosomal RNA genes which are known as 16S rDNA. PBMCs were isolated from 40 patients with ReA and 10 healthy controls. Clinical, laboratory and radiological evaluations were carried out for all patients and controls. Bacterial DNA was extracted from the PBMCs and subjected to PCR amplification of the 16S rDNA gene followed by DNA sequencing and database comparative analysis. Bacterial DNA was detected in 16/40 (40%) patients and 3/10 (30%) healthy controls. No significant difference was detected between the PCR +ve and -ve groups of patients as regards arthritis, arthralgia, sacroiliitis, low back pain and enthesopathies (P>0.05), while a significant difference was detected in the PCR +ve females with gynaecological infection (P<0.05). A significant difference of the pattern of arthritis was also observed between the two groups of patients. Comparative analysis of 7 16S rDNA sequences from patients and controls using Basic Local Alignment Search Tool (BLAST) and the National Center for Biotechnology Information (NCB1) database revealed high % similarity with potential pathogens and nonpathogenic bacteria. Further studies are needed to establish the exact role of these organisms in the pathogenesis of ReA.

Frequency and phenotype of T helper 17 cells in peripheral blood and synovial fluid of patients with reactive arthritis.

OBJECTIVE: To analyze the frequency and phenotype of peripheral blood mononuclear cells (PBMC) and synovial fluid mononuclear cell (SFMC) T helper (Th)17 cells in reactive arthritis (ReA). METHODS: T cell surface phenotype and cytokine production were measured following stimulation, using 8-color flow cytometry. RESULTS: The percentages of interleukin 17 (IL-17)-positive CD4+ T cells were increased in SFMC of patients with ReA compared with PBMC. All IL-17+ cells were CD4+CD45RO+; in SFMC most expressed CCR6, but only 50% expressed CCR4. IL-17+ cells sometimes coexpressed IL-22 and/or interferon-γ, but not IL-10. CONCLUSION: These data support the hypothesis that Th17 cells are involved in ReA pathogenesis.

Enthesitis and related changes in the knees in seronegative spondyloarthropathies and skin psoriasis: magnetic resonance imaging case-control study.

OBJECTIVE: To describe enhanced magnetic resonance imaging (MRI) features and characteristic entheseal changes in the knees in patients with seronegative spondyloarthropathy (SpA). METHODS: The 56 patients included 30 with psoriatic arthritis, 5 with ankylosing spondylitis, 5 with reactive arthritis, 5 with ulcerative colitis (UC), 5 with Crohn's disease, and another 6 with skin psoriasis. Controls were 20 healthy subjects without knee complaints. MRI was performed in all participants, emphasizing entheseal sites. RESULTS: Both knees were studied in 45 (80.3%) patients and one knee in 11 (19.6%). MRI showed evidence of bone marrow edema in 13 (23.2%) patients, cartilaginous erosions in 18 (32.1%), and bone erosions in 9 (16.1%). Enthesitis was found in medial collateral ligaments in 18 (32.1%), lateral collateral ligaments in 8 (14.3%), posterior cruciate ligaments in 3 (5.35%), patellar tendon in 18 (32.1%), biceps femoris insertion in 3 (5.35%), medial patellofemoral ligaments (MPFL) in 5 (8.9%), and lateral patellofemoral ligament in 1 patient (1.8%). In the UC and Crohn's patients (n = 10), 2 had bone erosions and 5 had enthesitis. In the skin psoriasis group (n = 6), one had bone marrow edema; enthesitis was detected in 5 at the patellar tendon insertion and in one in the MPFL. Entheseal-related changes were absent in the controls. CONCLUSION: This is the first study showing entheseal-related changes in the knees in patients with inflammatory bowel disease or skin psoriasis without clinical arthritis. Enthesitis of the knee on MRI may be an early finding in SpA.

A case of Poncet disease diagnosed with interferon-gamma-release assays.

BACKGROUND: A 55-year-old, HLA-B27-positive Finnish woman presented with migratory, sterile polyarthritis. INVESTIGATIONS: Physical examination, chest radiography, serologic testing, microscopy, M. tuberculosis-specific interferon gamma enzyme-linked immunospot (ELISPOT) assay, smear and culture of synovial fluid for acid-fast bacilli, and PCR. DIAGNOSIS: The patient's assayed blood and synovial fluid lymphocytes were reactive, and the numbers of M. tuberculosis-specific T cells, as determined by ELISPOT, were twofold to sixfold higher in synovial fluid than in blood. Cultures for acid-fast bacilli remained negative, while PCR specific for DNA of the M. tuberculosis complex was positive in synovial fluid cells. These results suggested that the patient had either active or latent M. tuberculosis infection. This finding, coupled with the presence of polyarthritis, led to a diagnosis of Poncet disease. MANAGEMENT: Standard antituberculous therapy consisting of isoniazid, rifampicin and pyrazinamide was given for 2 months, followed by isoniazid and rifampicin for 4 months. Inflamed joints were treated with methylprednisolone injections. The polyarthritis resolved within 4 months of initiating antituberculous therapy.

Serum levels of tissue inhibitor of metalloproteinase-1 and periarticular bone loss in early rheumatoid arthritis.

We investigated the relationship between disease activity, serum biological mediators of joint damage, and periarticular bone loss in inflammatory arthritis. Patients with early inflammatory arthritis were recruited from a dedicated early arthritis clinic. At the time of recruitment, all had clinical evidence of synovitis. Patients were assessed at baseline and at 1-year follow-up. Periarticular and axial bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry. Serum levels of matrix metalloproteinase 1 and tissue inhibitor of metalloproteinases 1 (TIMP-1) were measured by enzyme-linked immunosorbent assay. A total 38 patients were included in the study. Twenty had rheumatoid arthritis (RA) and 18 had a seronegative spondylarthropathy (SpA). At baseline, periarticular hand BMD measurements were similar in RA and SpA. At 1 year, the mean periarticular hand BMD was significantly lower in RA (p < 0.05). Significant inverse correlations between both the Ritchie articular index and C-reactive protein levels and the change in periarticular hand BMD at 1 year were observed in RA (r = -0.792, p < 0.001 and r = -0.478, p = 0.045, respectively). Baseline TIMP-1 levels correlated with the change in periarticular hand BMD at 1 year in RA (r = 0.519, p = 0.02). At 1 year, radiographic measures of joint damage were highest in RA. Inverse correlations between the change in periarticular hand BMD and the changes in erosion score (r = -0.90, p = 0.04) were observed in patients demonstrating significant periarticular bone loss. Persistent disease activity was associated with increased periarticular bone loss in the hands in patients with RA, consistent with synovitis-mediated periarticular bone loss. The correlation between baseline TIMP-1 levels and periarticular bone loss over 1 year suggests that TIMP-1 may have utility as a biomarker of periarticular bone loss in early RA.

Evidence-based correlation between anti-streptolysin O serum titer and sacroiliac joint disorder.

OBJECTIVE: Poststreptococcal reactive arthritis (PSReA) is a nonsuppurative sequela of antecedent streptococcal infection, and can be investigated when detecting the anti-streptolysin O (ASO) titer. The relationship between ASO titer and involvement of the peripheral synovial joints has been examined in PSRA, but data are sparse for the sacroiliac (SI) joint. Quantitative SI joint scintigraphy has been used clinically to detect active SI joint disorders, but not for PSReA. METHODS: A total of 84 subjects were recruited; mean age at enrollment was 23 years (range 18.0-36.4 yrs). All subjects were examined for ASO titer levels (range 25-520 IU/ml) and SI joint imaging, determined by sacroiliac to sacrum (SI/S) ratio derived from SI scintigraphy. RESULTS: Most of the subjects with high ASO titer had unclassified or undifferentiated arthritis. Good correlation between the ASO titer and the SI/S ratio was determined statistically using Pearson correlation coefficients. The relationships between ASO titer and SI/S ratio at various locations (laterality: left, right; location of part: upper, middle, lower) were found to be significantly correlated using generalized estimating equations. After adjustment for potential confounders, a highly significant association was determined between ASO titer and SI/S ratio (p < 0.0001), with an increase of 1 IU/ml of titer resulting in a significant increase in SI/S ratio by 0.0008 units. Age was significantly associated with SI/S ratio (p = 0.0022), with each extra year increasing the ratio by 0.0074. CONCLUSION: Our findings demonstrate a high correlation between SI joint involvement and high ASO titers. Subjects with SI joint involvement should be advised to have an ASO titer examination and quantitative SI joint scintigraphy.

Frequency of recent parvovirus infection in patients examined for acute reactive arthritis. A study with combinatorial parvovirus serodiagnostics.

OBJECTIVE: To determine the causative role of human parvovirus B19 as a preceding infection in patients examined for acute reactive arthritis (ReA). METHODS: Sixty adult patients with acute arthritis were screened for evidence of triggering infections. In all patients, cultures of stool specimens and of Chlamydia trachomatis in urethra/cervix, and/or bacterial serology were studied. The timing of primary infection of human parvovirus B19 was determined by measurement in serum of VP2-IgM, VP2-IgG, epitope-type specifity of VP2-IgG, and avidity of VP1-IgG. RESULTS: Median time from onset of joint symptoms to the rheumatological consultation was five weeks (range 1-62). Of the 60 patients, 35 fulfilled the diagnostic criteria for ReA; in the remaining, the diagnosis was unspecified arthritis (UA). Thirty-six patients had antibodies for the B19 virus. Occurrence of these antibodies did not differ significantly between ReA and UA groups (P = 0.61). Of these 36 patients, 34 had a pre-existing immunity to the B19 virus. Of the two other patients, one had rash and self-limiting polyarthritis with serological evidence of B19 primary infection, and the other had arthritis of the lower extremities with serological evidence of a convalescence period after the B19 primary infection. The latter patient also had antibodies to Yersinia, with a clinical picture typical for ReA. CONCLUSION: In patients examined for acute ReA, the frequency of recent B19 virus infection was 3.3% (2 out of 60). The diagnostic utility of the presented methodology, by using a single serum sample, was evident.