Reactive arthritis: Clinical sciences

Reactive arthritis, formally known as Reiter syndrome, belongs to a group of conditions called seronegative spondyloarthropathies. Seronegative means that the autoantibody called rheumatoid factor or RF is absent. Reactive arthritis is associated with autoimmune inflammation of joints that usually develops after genitourinary infections, most commonly chlamydia and gonorrhea; or intestinal infections, usually salmonella or shigella. Keep in mind that in most cases, this inciting infection is asymptomatic!

Okay, if your patient presents with chief concerns suggesting reactive arthritis, first, you should perform a focused history and physical.

Reactive arthritis doesn't just affect the joints, so don’t let the name fool you! Your patient will typically report pain in the large joints of the lower extremities, including knees, ankles, and feet. Keep in mind that the pain is usually asymmetric! Additionally, they will report systemic symptoms like fatigue, malaise, and low-grade fever; with possible ocular symptoms, such as burning of the eyes.

Additionally, this condition can affect almost any genitourinary structure, including the urethra, bladder, cervix, and prostate. They might also report recent genitourinary symptoms, like dysuria and urethral discharge; or gastrointestinal symptoms, such as diarrhea. Typically, symptoms of reactive arthritis occur several days to weeks after the inciting infection.

Additionally, the physical examination may reveal a tender lower extremity joint with effusion; and tenderness in the sacroiliac joint. You may also observe several extra-articular manifestations, such as enthesitis, or inflammation of the attachment sites of tendons to bones; as well as dactylitis, also known as sausage fingers.

Look out for common dermatologic findings, like nail pitting and onycholysis, where the nail separates from the nail bed. You may also notice keratoderma blennorrhagicum, which causes psoriatic nodules on the palms and soles; or oral ulcers. They may also present with other ophthalmologic findings, including simple conjunctivitis as well as anterior uveitis, which involves inflammation of the front eye chamber with the iris and ciliary body. In rare cases, your patient may have cardiac involvement with conduction disturbances and valvular dysfunction.

Now, here’s a high-yield fact! To help recall the classic triad of conjunctivitis, urethritis, and arthritis commonly observed in reactive arthritis, remember the phrase CAN’T SEE, CAN’T PEE, and CAN’T CLIMB A TREE! Note that this triad is only present in about one third of cases, so be on the lookout for other manifestations too!

With these findings, you should suspect inflammatory or infectious arthritis.

Your next step is to obtain labs, such as CBC, inflammatory markers, like ESR and CRP, rheumatoid factor, ANA, and HLA-B27. Additionally, you might want to order an X-ray of the affected joints.

Laboratory results will typically show a CBC with leukocytosis and anemia. You will also see marked elevation of ESR and CRP, as well as a negative ANA and rheumatoid factor. Finally, some individuals might present with positive HLA-B27. If you did order imaging, X-rays of affected joints may reveal linear or fluffy periostitis of the distal tibia or fibula, as well as calcaneal enthesitis and spurring. At this point, you should suspect reactive arthritis.