Chapter 25: RHEUMATOLOGY

ARTHRITIC CONDITIONS

ARTHROCENTESIS (JOINT ASPIRATION) PEARLS

If there is even the slightest question of a septic arthritis in a child, you must order an arthrocentesis (joint aspiration). It’s cheap, fairly painless, and extremely helpful. Please keep in mind that the numbers are quite different from those used to evaluate CSF during a meningitis workup. Some pearls are listed below to help guide you on questions in which arthrocentesis has already been done.

• YELLOW FLUID: NORMAL
• POSITIVE GRAM STAIN: Treat for an infection, regardless of the numbers.
• WBC < 200: NORMAL
• WBC < 2000: Consider TRAUMA. Fluid can be clear, yellow, or bloody.
• WBC > 2000: Consider an inflammatory OR infectious etiology. If the Gram stain is positive, treat!
• WBC ~ 5000:
  • Consider LUPUS (SLE).
  • Consider RHEUMATIC FEVER, but also look for mention of LOW or DECREASED viscosity.
• WBC > 50,000: Likely SEPTIC ARTHRITIS.
• JRA: WBC around 15,000 but LOW/DECREASED viscosity.

JUVENILE IDIOPATHIC ARTHRITIS (JRA, JIA)

KNOW JUVENILE IDIOPATHIC ARTHRITIS (AKA JUVENILE RHEUMATOID ARTHRITIS or JRA) WELL! The diagnosis requires knowing quite a few details. The child should have been under the age of 16 at the time of symptom onset. Symptoms must be present for at least 6 WEEKS before the diagnosis can be made. In children, if arthritis is present it is more common in the LARGE joints and rheumatoid nodules are much less common when compared to adults. A positive rheumatoid factor indicates a worse prognosis. Do NOT order a rheumatoid factor for diagnostic purposes. It can help with prognosis/subtyping, but a negative RF does NOT rule out RA.

• OLIGOARTICULAR JIA (OLIGOARTHRITIS AKA PAUCIARTICULAR JUVENILE IDIOPATHIC ARTHRITIS): This refers to JRA that affects 4 OR FEWER JOINTS, and is the more common type of JRA (>50%). ANA is often present but other markers such as RF are usually negative. It’s more common in younger girls and is associated with chronic uveitis. Since visual complaints may be absent, patients need to have regular eye exams. Boys have a better prognosis.
  • MNEMONIC: The O’s for OligO look like EYES and need regular eye exams because it is the more serious subtype.
• POLYARTICULAR JIA (POLYARTHRITIS): This refers to JIA that affects 5 OR MORE JOINTS. This is also more common in young girls. Systemic symptoms outside of the joints are not common.
• SYSTEMIC (AKA STILL’S DISEASE): This is equally common in boys and girls. There are many classic symptoms and findings of which to be aware, including an episodic, salmon-colored “EVANESCENT RASH.” Patients may also have an extremely high LEUKOCYTOSIS (> 30K), with spiking fevers, lymph­adeno­pathy, and possible hepatosplenomegaly. Patients may also have pleurisy, pericarditis, and the Koebner phenomenon (linear skin lesions appearing along a site of injury, rubbing, or scratching). Serum markers are NEGATIVE.
  • PEARL: If everything else fits and the patient doesn’t have an arthritis, go ahead and pick this diagnosis! The other symptoms are commonly present well before the arthritis component kicks in.
  • PEARL: This can be a difficult diagnosis to make and is often missed in clinical practice and on the pediatric board exam. Please be VERY, VERY comfortable with this topic.
  • PEARLS: In comparison to leukemia, pain is in the morning (not at night), pain is in the joints (not the bone), mild hematologic anomalies (not severe), symptoms wax and wane (not persistent/‌worsening), symptoms are insidious in onset (not acute), and JIA may have a rash. BOTH can have lymphadenopathy and hepatosplenomegaly. In comparison to septic arthritis, remember the insidious onset of symptoms for JIA (not acute).

Treatment should be directed towards underlying synovitis and inflammation. Initial treatment for polyarthritis should start with disease-modifying antirheumatic drugs (DMARDs) such as methotrexate or a tumor necrosis factor (TNF) inhibitor in addition to methotrexate for more severe disease. Start with an NSAIDS monotherapy trial for 1-2 weeks for mild-moderate oligoarticular JIA or systemic JIA, If no improvement, move on to the other treatment options.

• PEARL: Children receiving methotrexate should be supplementing with folic acid or leucovorin (folinic acid).
  • PEARL: Long term, high dose use of steroids should be avoided for patients with JIA. Short term, low dose steroids may be helpful in some patients, but DMARDs such as anti-TNF agents are the preferred treatment for children with JIA.