Reactive arthritis: symptoms, causes and treatment

By Cristiano Antonino On Jan 19, 2023

Reactive arthritis is an acute, non-purulent inflammation of the joints, which is caused by a localised infection affecting other parts of the body

This type of inflammation generally occurs 1-6 weeks after the infection, which is often sustained by microorganisms affecting the intestinal tract or genito-urinary tract.

It is a rheumatologic disease that falls into the group of seronegative spondyloarthritis, along with others, because it shares some common distinguishing features, such as positivity for the HLA-B27 antigen and negativity for rheumatoid factor.

Reactive arthritis or Reiter’s syndrome

In some cases the disease is also called Reiter’s syndrome.

In particular, it is a specific form of long-lasting reactive arthritis, which is often accompanied by:

arthritis (inflammation of the joints);
conjunctivitis;
urethritis (inflammation of the urinary tract).

Inflammation of the joints usually develops in people between the ages of 18 and 40, rarely in children or the elderly.

It can occur in women and men, if it is an infection of the gastrointestinal tract, when it occurs in the genitourinary tract it is more common in men.

Every year, this discomfort affects about 1-30 individuals per 100,000 inhabitants.

Septic arthritis

It is important not to confuse reactive arthritis with septic arthritis.

The reasons are as follows:

septic arthritis is a disease in which the pathogenic micro-organism is located directly inside the joint and can be found by analysing the synovial fluid;
in reactive arthritis, the micro-organism causes infection of the mucous membranes of the intestinal or genitourinary tract and only then, especially in more genetically predisposed persons, can it cause non-purulent joint inflammation.

Symptoms include both articular and extra-articular manifestations

Articular manifestations generally concern the leg joints, which may present as

swollen,
reddened,
stiff,
warm,
painful.

Extra-articular manifestations include:

persistent tiredness
moderate fever,
weight loss,
conjunctivitis
and oral ulcers.

Causes

Joint-related illness is often caused by an infection of the gastrointestinal or genito-urinary tract.

The microbes often responsible for the infection are different and are distinguished according to the part of our body affected.

The genito-urinary tract:

Chlamydia trachomatis;
Ureaplasma urealyticum.

The digestive tract:

Shigella (flexneri, sonnei);
Yersinia (enterocolitica, pseudotuberculosis);
Salmonella (all serotypes);
Campylobacter (jejuni, fetus, lari).

After infection, our immune system may also consider joint and extra-articular structures as targets to fight.

So our antibodies, in addition to fighting the infection, may also target structures within our own body.

It happens only rarely and generally affects genetically more predisposed people, such as those with the HLA-B27 antigen.

Reactive arthritis, the risk factors

The main risk factor that can lead to the development of the disease is the presence of the HLA-B27 antigen.

60-85% of patients who develop reactive arthritis are HLA-B27 positive.

Human leukocyte antigens (HLA -Human leukocyte antigen) are proteins that allow the immune system to discriminate between cells in the body and foreign cells.

Each of us has a specific HLA antigen combination, present on the surface of leukocytes and other cells.

Thus, possessing the HLA-B27 antigen only predisposes to the onset of reactive arthritis and other autoimmune diseases.

The HLA-B27 antigen increases the risk of causing reactive arthritis up to 50-fold following infection of the intestinal or genito-urinary tract.

Diagnosis

To diagnose this disease, one proceeds by means of anamnesis and on the basis of the specific clinical picture of the case.

How to treat reactive arthritis

Anti-inflammatory drugs are sufficient to treat arthritis that presents in a mild form.

For more severe arthritis that is refractory to treatment with anti-inflammatory drugs, the doctor may prescribe immunosuppressive drugs (sulfasalazine, azathioprine, methotrexate). In some cases, if the severity is considerable, apremilast, a phosphodiesterase 4 inhibitor, may be recommended.

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