MEDizzy - A 9-year-old girl presents to her pediatrician with a 3-week

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RHEUMATOID ARTHRITIS

A 9-year-old girl presents to her pediatrician with a 3-week history of spiking fevers at night up to 39.4°C (102.9°F). The fevers usually subside with acetaminophen or ibuprofen but eventually return. She has also been complaining of pain in her legs. Furthermore, she has developed a salmon-colored rash on her chest and arms that flares every time she has a fever spike. Her temperature is 38.3°C (100.9°F), heart rate is 96/min, and blood pressure is 104/56 mm Hg. Bilateral anterior cervical and axillary lymphadenopathy is present. Cardiac examination reveals a regular rate and rhythm with no murmurs or rubs. The abdomen is soft and nontender, and her liver is palpable 3 cm below the costal margin. Her right knee and left ankle are swollen and warm, with decreased range of motion. Which of the following is the most likely diagnosis?

ExplanationThe correct answer is B. The combination of several weeks of high-spiking fevers, arthritis, and salmon-colored rash is highly suggestive of systemic-onset juvenile rheumatoid arthritis (JRA). The salmon-colored macular rash is activated by heat and is frequently found in warm areas of the body such as the axilla and the waist. The rash is commonly triggered by a fever spike, but subsides when the temperature returns to normal. Physical examination findings in systemic-onset JRA include lymphadenopathy, hepatomegaly, and splenomegaly. There is no specific test for JRA, so the diagnosis is typically made by clinical presentation. Answer A is incorrect. Acute rheumatic fever (ARF) is a complication of Group A streptococcal pharyngitis. It is characterized by five major criteria: migratory arthritis of the large joints, carditis, rash, chorea, and subcutaneous nodules. The rash of ARF is erythema marginatum, a pink, nonpruritic rash with sharply defined borders and central clearing that predominantly occurs on the trunk. Fever is one of the minor criteria of ARF, along with arthralgias and previous rheumatic heart disease. Diagnosis of ARF by Jones’ criteria requires the presence of two major, or one major and two minor, criteria in addition to evidence of a recent streptococcal infection. Answer C is incorrect. Parvovirus can also cause fever, rash, and arthritis, and is often considered in the differential diagnosis of systemic-onset JRA. However, viral infections rarely cause the spiking fevers that are seen in patients with systemic-onset JRA. In addition, the rash of parvovirus is classically a “slapped-cheek” appearance. Viral exanthems tend to persist regardless of temperature, as opposed to the rash of JRA that fluctuates with fever. Answer D is incorrect. Classic Reiter’s syndrome is characterized by a classic triad of uveitis, urethritis, and arthritis (“can’t see, can’t pee, can’t climb a tree”). Reiter’s syndrome is typically caused by Chlamydia trachomatis. It is one of the spondyloarthropathies in which patients have axial and sacroiliac inflammatory arthritis. Patients may also have asymmetric involvement of large peripheral joints, particularly of the lower limbs.