Single joint pain is not rheumatoid? There are times when "standards" go wrong...

*For medical professionals only

Rheumatoid arthritis is a chronic autoimmune disease

Recently, a case of single-joint rheumatoid arthritis of the elbow confirmed by synovial tissue biopsy in middle-aged women was reported on BMJ Case Reports

Case profile

▌ Basic information

A middle-aged woman who underwent cervical C4-C6 posterior fusion surgery in her right arm and neck 5 years ago due to a work injury, and 1 year ago, due to suppuration of a neck wound, she was hospitalized again for cervical spine debridement surgery

Physical examination: body temperature 36.

"Dial the clouds to see the sun", auxiliary inspection to help

▌ Laboratory tests

Blood count: white blood cells (WBCs) 6.

▌ Imaging examination

X-rays of the right elbow show anterior and posterior fat pad displacement, suggesting an intra-articular effusion

Figure 1: Right elbow MRI scan image

▌ Tissue biopsy

Synovial tissue biopsy shows hyperplasia with active lymphoplasmic cells, occasionally multinucleated giant cells, and focal acute inflammation of fibrinosis
.

Synovial tissue and synovial fluid cultures are negative
.

Synovial fluid examination under a polarized microscope did not reveal crystals
.

Fig.
2: Right synovial biopsy: papillary chronic synovitis in different areas of A-C, with a large number of lymphoplastic infiltrates, lymphatic follicles, and focal fibrin exudates (H&E 40×) in areas
B and C.

Synovial hyperplasia in the D region, massive lymphoplasmic infiltration, multinucleated giant cells, and acute fibrin exudate (below) (H&E 100×).


Synovial hyperplasia in the E region, lymphoplasmic infiltrates, and multinucleated giant cells (lower right) (H&E 100×
).

Higher magnification in the F-zone (H&E 400×)

Single joint inflammation, what kind of disease is it?

This middle-aged woman, who had manifestations of monoarthritis, had several names in her head in her head at that time: reactive arthritis, trauma, arthropathy caused by crystals, septic arthritis, osteoarthritis.
.
.

Which one is it? Don't worry, let's comb through
them one by one.

Reactive arthritis: is an arthritis that occurs after infection in certain specific areas (such as the intestine and genitourinary tract), and classic reactive arthritis refers only to a class of peripheral arthritis that occurs in the short term after infection of the genitourinary system or gastrointestinal tract in certain specific urogenital system or gastrointestinal tracts, and the patient does not have consistent clinical or radiographic manifestations
with reactive arthritis.

Traumatic arthritis: also known as traumatic arthritis, injury osteoarthritis, it is caused by trauma to the degeneration of joint cartilage degeneration and secondary cartilage hyperplasia, ossification into the main pathological changes, joint pain, mobility dysfunction as the main clinical manifestations of a disease
.

It can occur in any age group, but is more common in young adults and is more common in post-traumatic, unbalanced weight-bearing, and hypermobile joints
.

In this case, although the neck and right arm were traumatized, it was not until 3 years after the trauma that her right elbow developed swelling or fever, so it can also be ruled out
.

Crystal arthritis: also known as gouty arthritis
.

Due to purine metabolism disorders, urate accumulates in cartilage, joints, and subcutaneous tissues, and becomes "tophi" after a long time
.

More common in men, the most common site is usually in the first thumb joint, and in this patient's synovial fluid examination no evidence of sodium urate, dehydrated calcium pyrophosphate, or calcium oxalate crystals
.

Septic arthritis: it is an arthritis that is directly infected by purulent bacteria and causes joint destruction and loss of function, also known as bacterial arthritis or septic arthritis
.

It can occur at any age, but is more likely to occur in children, elderly frail, and chronic arthropathy patients, in which synovial fluid and tissue culture are negative, ruling out the diagnosis
of septic arthritis.

Osteoarthritis: patients have no radiological evidence of osteoarthritis on plain x-rays of the right elbow, and although synovial biopsy in patients with inflammatory osteoarthritis may present as nonspecific synovitis, it is highly unlikely that active lymphoplastic infiltrates and multinucleated giant cells
will occur.

After ruling out other causes of the above symptoms, the patient was eventually diagnosed with monarticular rheumatoid arthritis
.

The patient in this case is single-jointly affected and although not fully compliant with the ACR/EULAR classification criteria for rheumatoid arthritis, she has a positive anti-CCP antibody and synovial biopsy results, which are consistent with rheumatoid arthritis
.

It must be emphasized that classification criteria are not diagnostic criteria, and although classification criteria help to provide patients with a specific diagnosis, these criteria are primarily intended to create different, relatively uniform clinical research cohorts
.

▌ Results and follow-up

The patient, who had a neck wound with staphylococcus epidermidis infection during her hospitalization, was discharged after receiving a full course of antibiotics, after which she began taking sulfasalazine twice a day for 1 g
.

However, due to the inability to tolerate sulfasalazine, follow-up treatment was changed to methotrexate 7.
5 mg per week
.

She responded well
to this treatment.

After 7 months of discharge, he recovered well, and the pain and swelling in his right elbow improved
significantly.

During the follow-up period, there were no other peripheral joint involvements, nor were there extra-articular manifestations
.

At the end of the case, we concluded:

In summary, single-joint rheumatoid arthritis is rarely seen clinically, especially the elbow joint as the main clinical manifestation
.

In rheumatoid arthritis, elbow involvement usually presents as bilateral slow involvement, which is an advanced manifestation
of the disease.

Any patient with monoarthritis should be carefully examined to rule out infection, trauma, crystal deposition, or tumors, so that early treatment can be initiated to avoid disease progression and disability
.

After excluding infectious causes and other causes of arthritis, testing
of disease-modifying antirheumatic drugs (DMARDs) should be considered in patients with inflammatory arthritis.

In addition, this case highlights the importance of synovial tissue analysis in patients with chronic inflammatory simple arthritis, particularly in patients whose clinical diagnosis is not obvious and who exclude other diseases such as malignancy, sarcoidosis, and other invasive/inflammatory or chronic infectious diseases in the
differential diagnosis.

[1] Santiago A, Crespo-Ramos SM, Correa-Rivas M,Monarticular rheumatoid arthritis of the elbow.
BMJ Case Rep.
2022 Mar 7; 15(3):e246863.

[2] Smolen JS, Aletaha D, McInnes IB.
Rheumatoid arthritis.
Lancet 2016; 388:2023–38.

[3] Bergstra SA, Chopra A, Saluja M, et al.
Evaluation of the joint distribution at disease presentation of patients with rheumatoid arthritis: a large study across continents.
RMD Open 2017; 3:e000568.

Source of this article: Rheumatic Immunity Channel of the Medical Community

This article is written by Jenny

This article is reviewed: Chen Xinpeng, Deputy Chief Physician

Editor-in-charge of this article: Orange