Introduction
Background
Reactive arthritis (ReA), also known as Reiter syndrome, is an autoimmune condition that develops in response to an infection. In 1916, Hans Reiter described the triad of nongonococcal urethritis, conjunctivitis, and arthritis in a young German officer with bloody dysentery.1 In 1916, Fiessinger and Leroy described 4 patients with what they called oculo-urethro-synovial syndrome and associated the syndrome with an outbreak of Shigella dysentery.
Since then, many cases of what is now known as reactive arthritis have been described. The older term Reiter's syndrome, used in the past to describe the same clinical presentations, is being used less frequently. This is because Reiter was a physician leader of the Nazi party in Germany during World War II and authorized medical experiments on prisoners in concentration camps.2
Reactive arthritis has been associated with gastrointestinal infections with Shigella , Salmonella , and Campylobacter species and other microorganisms, as well as with genitourinary infections (especially with Chlamydia trachomatis).
Outbreaks of enteric Reiter syndrome have been reported aboard military vessels, cruise ships, and vessels transporting immigrants to the United States. In 1967, the term reactive arthritis was first used in cases associated with Yersinia gastroenteritis. A strong association with human leukocyte antigen (HLA)–B27 was found. This finding helped to confirm the concept of an incomplete Reiter syndrome, in which arthritis can occur in the absence of urethritis and conjunctivitis. Because of the association with HLA-B27 and its clinical overlap with ankylosing spondylitis and psoriatic arthritis, reactive arthritis is classified as a type of seronegative spondyloarthropathy.
In this article, reactive arthritis encompasses the older concepts of complete and incomplete Reiter syndrome and a clinical syndrome of arthritis with or without extra-articular features that develop within one month of infectious diarrhea or genitourinary infection.
Pathophysiology
Reactive arthritis usually develops 2-6 weeks after a genitourinary or gastrointestinal infection. Recent evidence indicates that a preceding Chlamydia respiratory infection may also trigger reactive arthritis.3 About 10% of patients do not have a preceding symptomatic infection.
Inflammation of joints, entheses, axial skeleton, skin, mucous membranes, gastrointestinal tract, and eyes may occur. Results for HLA-B27 are positive in 65%-96% of patients (average, 75%) with reactive arthritis. The likelihood of developing reactive arthritis is increased 50-fold in patients who are HLA-B27–positive, but this syndrome can also occur in patients who are HLA-B27 negative.
Patients with HLA-B27, as well as those with a strong family clustering of the disease, tend to develop more severe and long-term disease. The frequency of reactive arthritis after enteric infection averages 1%-4% but varies greatly, even among outbreaks of the same organism.
The mechanism of the interaction of the inciting organism with the host (often HLA-B27–positive) leading to the development of reactive arthritis is not known. It is unclear if microbial antigens cross-react with self-proteins, stimulating (molecular mimicry) and perpetuating a Th2-cell–mediated autoimmune response. Chronicity and joint damage have been associated with a Th2 cytokine profile that leads to decreased bacterial clearance.4
Synovial fluid cultures are negative for enteric organisms or Chlamydia species. However, a systemic and intrasynovial immune response to the organisms has been found with intra-articular antibody and bacterial reactive T cells. Furthermore, bacterial antigen has been found in the joints. Thus, the elements for an immune-mediated synovitis are present.
Molecular evidence of bacterial DNA (by polymerase chain reaction [PCR]) in synovial fluids has been found only in Chlamydia -related reactive arthritis, and one placebo-controlled trial of a tetracycline derivative (ie, lymecycline) showed a reduction in the duration of acute Chlamydia -related, but not enteric-related, reactive arthritis.5 This suggests that persistent infection may play a role, at least in some cases of chlamydial reactive arthritis. In a more recent trial, the combination of doxycycline and rifampin was superior to doxycycline alone in reducing morning stiffness and swollen and tender joints in patients with undifferentiated spondyloarthropathy.6
The Toll-like receptors (TLRs) recognize different extracellular antigens as part of the innate immune system. TLR-4 recognizes gram-negative lipopolysaccharide (LPS). Studies in mice and humans showed abnormalities in antigen presentation due to down-regulation of TLR-4 costimulatory receptors in patients with reactive arthritis. More recent studies implicated TLR-2 polymorphism associated with acute reactive arthritis; however, its role is still disputed.4,7
The role of HLA-B27 in this scenario remains to be defined but, as discussed elsewhere (Ankylosing Spondylitis and Undifferentiated Spondyloarthropathies), molecular mimicry, presentation of pathogenic peptides, and an altered host response to the bacteria are all possible.
Reactive arthritis, including classic Reiter syndrome, can occur in patients infected with HIV or who have AIDS. This is likely because both conditions can be sexually acquired rather than being triggered by HIV. The course of reactive arthritis in these patients tends to be severe, with a generalized rash that resembles psoriasis, profound arthritis, and frank AIDS. The frequency of HLA-B27 is the same of that associated with non–AIDS-related reactive arthritis in a similar demographic group. This association points out the likely importance of CD8+ cytotoxic T cells compared to CD4+ helper T cells in the pathogenesis of reactive arthritis.
Frequency
International
Data on the incidence and prevalence of reactive arthritis are scarce, partly because of a lack of a disease definition and diagnosis criteria; these factors complicate differentiation of reactive arthritis from other arthritides.8 The reported annual incidence of reactive arthritis is approximately 30-40 cases per 100,000 adults, with a prevalence of 1%-7%, but this varies greatly among different geographic locations.9 Reports from Latin America, North Africa, India, and Thailand showed low prevalence, with minimal differences between countries.10,11
Mortality/Morbidity
Reactive arthritis typically follows a self-limited course, with resolution of symptoms by 3-12 months, even in patients who are acutely incapacitated. However, reactive arthritis has a high tendency to recur, particularly with ocular and urogenital inflammation. Individuals who are HLA-B27–positive are at a higher risk of recurrence. A new infection or other stress factor could cause reactivation of the disease.
About 15% of patients with reactive arthritis develop a long-term, sometimes destructive, arthritis or enthesitis or spondylitis. In a study by Amor et al (1994), 7 factors were analyzed as predictors of long-term outcome in spondyloarthropathies.12 The number of patients with reactive arthritis in this study was low, and a valid subgroup analysis was impossible. The presence of hip-joint involvement, an erythrocyte sedimentation rate (ESR) higher than 30, and unresponsiveness to nonsteroidal anti-inflammatory drugs (NSAIDs) probably portend a severe outcome or chronicity in reactive arthritis.
Race
As with other spondyloarthropathies, HLA-B27 and reactive arthritis are more common in white people than in black people.
Sex
Reactive arthritis following foodborne enteric infections is equally common in males and females. The male-to-female ratio of disease associated with venereally acquired infections is 9:1.
Age
Most patients with reactive arthritis are aged 20-40 years.
Clinical
History
Reactive arthritis usually develops 2-4 weeks after a genitourinary or gastrointestinal infection. Recent evidence indicates that a preceding respiratory infection with Chlamydia pneumoniae may also trigger the disease.3 About 10% of patients do not have a preceding symptomatic infection.
Both postvenereal and postenteric forms of reactive arthritis may manifest initially as nongonococcal urethritis. Mild dysuria, mucopurulent discharge, prostatitis and epididymitis in men, and vaginal discharge and/or cervicitis in women are other possible manifestations.
The onset of reactive arthritis is usually acute and characterized by malaise, fatigue, and fever. An asymmetrical, predominately lower-extremity, oligoarthritis is the major presenting symptom. Low-back pain occurs in 50% of patients. Heel pain is common because of enthesopathies at the Achilles or plantar aponeurosis insertion on the calcaneus. The complete Reiter triad of urethritis, conjunctivitis, and arthritis may occur.
Physical
* Joints, axial skeleton, entheses
o Peripheral joint involvement associated with reactive arthritis is typically asymmetric and usually affects the weight-bearing joints (ie, knees, ankles, hips), but the shoulders, wrists, and elbows may also be affected.
o In more chronic and severe cases, the small joints of the hands and feet may also be involved. As in other spondyloarthropathies, dactylitis (ie, sausage digits) may develop.
o While 50% of patients with reactive arthritis may develop low-back pain, most physical examination findings in patients with acute disease are minimal except for decreased lumbar flexion. Patients with more chronic and severe axial disease may develop physical findings similar to ankylosing spondylitis.
o As with other spondyloarthropathies, the enthesopathy of reactive arthritis may be associated with findings of inflammation (ie, pain, tenderness, swelling) at the Achilles insertion. Other sites include the plantar fascial insertion on the calcaneus, ischial tuberosities, iliac crests, tibial tuberosities, and ribs.
* Skin and nails
o Keratoderma blennorrhagica on the palms and soles is indistinguishable from pustular psoriasis and is highly suggestive of chronic reactive arthritis.
o Erythema nodosum may develop but is uncommon.
o Nails can become thickened and crumble, resembling mycotic infection or psoriatic onychodystrophy, but nail pitting is not observed.
o Circinate balanitis may also develop.
* Other mucosal signs and symptoms: Painless shiny patches in the palate, tongue, and mucosa of the cheeks and lips have been described.
* Ocular findings
o Conjunctivitis is part of the classic triad of Reiter syndrome and can occur before or at the onset of arthritis.
o Other ocular lesions include acute uveitis (20% of patients), episcleritis, keratitis, and corneal ulcerations. The lesions tend to recur.
* Enteric infections
o Enteric infections may trigger reactive arthritis. Pathogens include Salmonella, Shigella, Yersinia, and Campylobacter species. The frequency of reactive arthritis after these enteric infections is about 1%-4%. Other enteric bacteria that have been associated with reactive arthritis include Clostridium difficile,13 Escherichia coli, and Helicobacter pylori.14
o Some patients with reactive arthritis continue with intermittent bouts of diarrhea and abdominal pain. Lesions resembling ulcerative colitis or Crohn disease have been described when ileocolonoscopy is performed in patients with established reactive arthritis.13
* Other manifestations
o Other manifestations of reactive arthritis include mild renal pathology with proteinuria and microhematuria.
o In severe chronic cases, amyloid deposits and immunoglobulin A (IgA) nephropathy have been reported. Cardiac conduction abnormalities may develop, and aortitis with aortic regurgitation occurs in 1%-2% of reactive arthritis cases.
Causes
Reactive arthritis is usually triggered by a genitourinary or gastrointestinal infection.
Bacteria postulated to be potential causes of reactive arthritis include Ureaplasma urealyticum, C trachomatis L2b serotype,15 beta-hemolytic streptococci,16 and Mycobacterium tuberculosis.17 In addition, case reports have described reactive arthritis after vaccination with live vaccines18,19 and after intravesical therapy with Bacillus Calmette-Guérin (BCG)Differential Diagnoses
Ankylosing Spondylitis and Undifferentiated Spondyloarthropathy
Psoriatic Arthritis
Gonococcal Arthritis
Rheumatic Fever
Gout
Rheumatoid Arthritis
Inflammatory Bowel Disease
Septic Arthritis
Workup
Laboratory Studies
* The values of acute-phase reactants, including erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), are usually elevated markedly but later return to the reference range when the inflammation subsides.
* Other laboratory findings include a normocytic normochromic anemia along with mild leukocytosis and thrombocytosis during the acute phase. IgA antibodies to specific bacterial antigens have been reported. Urinalysis may reveal aseptic pyuria.
* Synovial fluid analysis reveals a high WBC count, most often with elevated polymorphonuclear leukocytes acutely. Gram stain and culture results are negative and are necessary to exclude septic arthritis. Microbial components and antigens have been identified in joint fluid using sophisticated laboratory techniques.
* Throat, stool, or urogenital tract cultures can be performed in an attempt to isolate the causative organism. Other serologic techniques for the detection of Chlamydia species, including PCR, may be considered.
* Test results for rheumatoid factor and antinuclear antibodies are negative.
Imaging Studies
* Radiography
o Early in the disease process, radiography reveals no abnormalities.
o In more advanced or long-term reactive arthritis, periosteal reaction and proliferation at sites of tendon insertion are visible.
o Exuberant plantar spurs are a common sign in long-term reactive arthritis.
o In the hands and feet, marginal erosions with adjacent bone proliferation occur.
o Spinal radiographic findings include sacroiliitis and syndesmophytes. Sacroiliitis occurs in less than 10% of acute cases but develops in half of patients with chronic severe disease.
o Syndesmophytes are usually asymmetrical and are found most commonly in the thoracolumbar region.
o Severe ankylosing spondylitis occurs in less than 5% of cases.
* MRI: MRI of the sacroiliac joints may reveal disease earlier than conventional radiography.
Other Tests
* ECG should be performed in patients with a prolonged course of reactive arthritis to evaluate for conduction disturbances.
* HLA-B27 testing results are positive in 65%-96% of cases. HLA-B27 testing is not necessary in classic Reiter syndrome but may be helpful to support the diagnosis of reactive arthritis in patients with joint-restricted symptoms.
Procedures
* Needle aspiration of a joint may be necessary to rule out septic or crystal-induced arthritis.Treatment
Medical Care
The treatment of reactive arthritis is depends on the severity of symptoms.
* Nonsteroidal anti-inflammatory drugs
o NSAIDs are the foundation of therapy. These agents should be used regularly to achieve a good anti-inflammatory effect.
o The choice of a specific agent depends on the individual response to treatment, although the general impression is that indomethacin has greater potency.
o Physical therapy needs to be implemented to help reduce pain and to avoid muscle wasting in severe cases of reactive arthritis.
* Corticosteroids
o These agents can be used as either intra-articular injection or systemic therapy.
o Joint injections can produce long-lasting symptomatic improvement and help avoid the use of other systemic therapy. Sacroiliac joints can be injected, usually under fluoroscopic guidance.21
o Systemic corticosteroids can be used, particularly in patients in whom NSAIDs elicit a poor response or in those who develop adverse effects related to their use. The starting dose is guided by a patient's symptoms and objective evidence of inflammation. Prednisone 0.5-1 mg/kg/d can be used initially and tapered according to response.
* Antibiotics
o The current concepts on the pathogenesis of reactive arthritis indicate that an infectious agent is the trigger of the disease, but antibiotic treatment does not change the course of the disease, even when a microorganism is isolated. In these cases, antibiotics are used to treat the underlying infection, but specific treatment guidelines for reactive arthritis are lacking. However, in chlamydia-induced reactive arthritis, studies have suggested that the appropriate treatment of the acute urogenital infection can prevent reactive arthritis and that treatment of acute reactive arthritis with a 3-month course of tetracycline reduces the duration of illness. No evidence indicates that antibiotic therapy benefits enteric-related reactive arthritis or chronic reactive arthritis of any cause.
o Lymecycline was studied in a double-blind placebo-controlled study of patients with chronic reactive arthritis for a treatment period of 3 months.4 The duration of illness was significantly decreased in patients with chlamydia-induced disease, as opposed to those with disease triggered by enteric infections.
o Azithromycin was shown to be ineffective in a placebo-controlled trial.22 Nevertheless, in a recent abstract presentation, azithromycin or doxycycline in combination with rifampin for 6 months was reported to be significantly superior to placebo and significantly improved symptoms associated with chlamydia–induced reactive arthritis.23
o Quinolones have been studied because of their broad coverage, but no clear benefit has been reported.24
o More studies are needed before definite recommendations can be made for the role of antibiotics in the management of reactive arthritis.
* Disease-modifying antirheumatic drugs
o In patients with chronic symptoms or in patients with persistent inflammation despite the use of the agents mentioned above, other second-line drugs may be used. Clinical experience with these so-called disease-modifying antirheumatic drugs (DMARDs) has been mostly in rheumatoid arthritis and in psoriatic arthritis. DMARDs have also been used in reactive arthritis, although their disease-modifying effects in the reactive arthritis setting are uncertain.
o Sulfasalazine may be beneficial in some patients. The use of this drug in reactive arthritis is of interest because of the finding of clinical or subclinical inflammation of the bowel in many patients. Sulfasalazine is more widely used in ankylosing spondylitis. In a 36-week trial of sulfasalazine versus a placebo in the spondyloarthropathies, patients with reactive arthritis who were taking sulfasalazine had a 62.3% response rate compared to 47.7% for the placebo group in peripheral arthritis (P = 0.09).25
o Methotrexate can be used in patients who present with rheumatoidlike disease. Several reports have shown good response, but controlled studies are lacking. Reports also describe the use of azathioprine and bromocriptine in reactive arthritis, but, again, large studies have not been published.26,27 Patients with reactive arthritis and HIV/AIDS should not receive methotrexate or other immunosuppressive agents.
o Although biologic agents such as TNF-blockers have been demonstrated to be beneficial and formally approved for the treatment of psoriatic arthritis and ankylosing spondylitis, double-blind, randomized trials have not been performed to prove clinical benefit in reactive arthritis or in undifferentiated spondyloarthropathy. Case reports using the chimeric monoclonal antibody infliximab have shown potential efficacy in symptom relief in patients in whom other therapies failed.28,29,30
Surgical Care
No surgical treatment of reactive arthritis is recommended.
Consultations
A rheumatologist should be consulted for confirmation of diagnosis and formulation of management plan. Consultation with a urologist may be necessary if particularly prominent genitourinary manifestations develop. An ophthalmologist may be consulted to confirm the diagnosis and to treat the ophthalmologic manifestations of reactive arthritis.
Activity
Physical therapy may be instituted to avoid muscle wasting and to reduce pain. Activities should otherwise be as tolerated by the patient.
Medication
The goals of pharmacotherapy are to reduce morbidity, to prevent joint damage, and to alleviate extra-articular disease.
Nonsteroidal anti-inflammatory drugs (NSAIDs)
Several NSAIDs are available and have similar effectiveness, although indomethacin may be more effective in the spondyloarthropathies. These agents are used to treat symptoms. Cyclooxygenase-2 (COX-2)–specific inhibitors can be used in patients at high risk for GI complications.
Ibuprofen (Motrin, Advil)
Inhibits inflammatory reactions and pain by decreasing prostaglandin synthesis.
* Dosing
* Interactions
* Contraindications
* Precautions
Adult
400-600 mg PO qid or 800 mg PO tid
Pediatric
Not established
* Dosing
* Interactions
* Contraindications
* Precautions
Coadministration with aspirin increases risk of inducing serious NSAID-related adverse effects; probenecid may increase concentrations and, possibly, toxicity of NSAIDs; may decrease effect of hydralazine, captopril, and beta-blockers; may decrease diuretic effects of furosemide and thiazides; monitor PT closely (instruct patients to watch for signs of bleeding); may increase risk of methotrexate toxicity; phenytoin levels may be increased when administered concurrently
* Dosing
* Interactions
* Contraindications
* Precautions
Documented hypersensitivity; peptic ulcer disease; recent GI bleeding or perforation; renal insufficiency; high risk of bleeding
* Dosing
* Interactions
* Contraindications
* Precautions
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
Caution in CHF, hypertension, and in PT with decreased renal and hepatic function; caution in anticoagulation abnormalities or during anticoagulant therapy
Indomethacin (Indocin, Indochron E-R)
Rapidly absorbed. Metabolism occurs in liver by demethylation, deacetylation, and glucuronide conjugation. Inhibits prostaglandin synthesis.
* Dosing
* Interactions
* Contraindications
* Precautions
Adult
25-50 mg PO bid/tid
75 mg SR PO bid; not to exceed 200 mg/d
Pediatric
1-2 mg/kg/d PO divided bid/qid; not to exceed 4 mg/kg/d or 150-200 mg/d
* Dosing
* Interactions
* Contraindications
* Precautions
Coadministration with aspirin increases risk of inducing serious NSAID-related side effects; probenecid may increase concentrations and, possibly, toxicity of NSAIDs; may decrease effect of hydralazine, captopril, and beta-blockers; may decrease diuretic effects of furosemide and thiazides; may increase PT when taking anticoagulants (instruct patients to watch for signs of bleeding); may increase risk of methotrexate toxicity; phenytoin levels may be increased when administered concurrently
* Dosing
* Interactions
* Contraindications
* Precautions
Documented hypersensitivity; GI bleeding; renal insufficiency
* Dosing
* Interactions
* Contraindications
* Precautions
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
Acute renal insufficiency, hyperkalemia, hyponatremia, interstitial nephritis, and renal papillary necrosis may occur; increases risk of acute renal failure in patients with pre-existing renal disease or compromised renal perfusion; reversible leukopenia may occur (discontinue if persistent leukopenia, granulocytopenia, or thrombocytopenia occurs)
Tetracyclines
These agents are used to treat urethritis or cervicitis caused by chlamydial organisms. Some evidence shows that, in chlamydia-induced Reiter syndrome, tetracycline treatment may reduce duration and perhaps severity of illness. Collagenase inhibitors have been used to treat early rheumatoid arthritis.
Doxycycline (Bio-Tab, Vibramycin)
Inhibits protein synthesis and, thus, bacterial growth by binding to 30S and possibly 50S ribosomal subunits of susceptible bacteria.
* Dosing
* Interactions
* Contraindications
* Precautions
Adult
Urethritis or cervicitis: 100 mg PO bid 7d
Decrease severity: 100 mg PO bid for 8-12 wk
Pediatric
Not established
* Dosing
* Interactions
* Contraindications
* Precautions
Bioavailability decreases with antacids containing aluminum, calcium, magnesium, iron, or bismuth subsalicylate; tetracyclines can increase hypoprothrombinemic effects of anticoagulants; tetracyclines can decrease effects of PO contraceptives, causing breakthrough bleeding and increased risk of pregnancy
* Dosing
* Interactions
* Contraindications
* Precautions
Documented hypersensitivity; severe hepatic dysfunction
* Dosing
* Interactions
* Contraindications
* Precautions
Pregnancy
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
Photosensitivity may occur with prolonged exposure to sunlight or tanning equipment; reduce dose in renal impairment; consider drug serum level determinations in prolonged therapy; tetracycline use during tooth development (ie, <8 y) can cause permanent discoloration of teeth; Fanconilike syndrome may occur with outdated tetracycline
Corticosteroids
These agents have anti-inflammatory properties and cause profound and varied metabolic effects. Corticosteroids modify the body's immune response to diverse stimuli.
Prednisone (Sterapred)
May decrease inflammation by reversing increased capillary permeability and suppressing PMN activity.
* Dosing
* Interactions
* Contraindications
* Precautions
Adult
0.5 mg/kg/d PO initially, taper according to response
Pediatric
Not established
* Dosing
* Interactions
* Contraindications
* Precautions
Coadministration with estrogens may decrease prednisone clearance; concurrent use with digoxin may cause digitalis toxicity secondary to hypokalemia; phenobarbital, phenytoin, and rifampin may increase metabolism of glucocorticoids (consider increasing maintenance dose); monitor for hypokalemia with coadministration of diuretics
* Dosing
* Interactions
* Contraindications
* Precautions
Documented hypersensitivity; viral infection; peptic ulcer disease; hepatic dysfunction; connective tissue infections; fungal or tubercular skin infections; GI disease
* Dosing
* Interactions
* Contraindications
* Precautions
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Precautions
Abrupt discontinuation of glucocorticoids may cause adrenal crisis; hyperglycemia; edema; osteonecrosis; myopathy; peptic ulcer disease; hypokalemia; osteoporosis; euphoria; psychosis; myasthenia gravis; growth suppression; infections may occur with glucocorticoid use
Aminosalicylic acid derivatives
These agents are used to reduce inflammation.
Sulfasalazine (Azulfidine, EN-tabs)
Acts locally in colon to decrease the inflammatory response and systemically inhibits prostaglandin synthesis.
* Dosing
* Interactions
* Contraindications
* Precautions
Adult
500 mg PO bid initially; 1000 mg PO bid
Pediatric
Not establishedFollow-up
Further Inpatient Care
Hospitalization of a patient with uncomplicated reactive arthritis is not indicated.
Deterrence/Prevention
Even when a causal microorganism is isolated, antibiotic therapy does not change the course of the disease.
Patient Education
For excellent patient education resources, visit eMedicine's Arthritis Center. Also, see eMedicine's patient education article Psoriatic Arthritis.
Miscellaneous
Medicolegal Pitfalls
* Septic arthritis must be ruled out if suspected before a diagnosis of reactive arthritis is made. Failure to appropriately treat septic arthritis in a timely manner could result in joint destruction. Medicolegal liability could result from this oversight.
* HIV/AIDS should be considered before instituting immunosuppressive therapy in severe cases of reactive arthritis.
