A 2-year-old girl is brought to the clinic for evaluation of left knee pain and fever. The knee pain began 2 months ago. At the time of onset, the patient and several other children at day care had cough and rhinorrhea, but only the patient developed joint pain. Movement is limited by pain in the morning but seems to improve in the afternoon. For the past month, she has had a daily fever and an erythematous macular rash over her chest around bedtime. Temperature is 36.1 C (97 F), blood pressure is 90/60 mm Hg, and pulse is 114/min. Physical examination shows swelling, erythema, and warmth of the left knee, with pain elicited on passive and active movement of the left hip. The patient can walk but has a slight limp. Laboratory results are as follows: Which of the following is the most likely diagnosis in this patient?

Question

A 2-year-old girl is brought to the clinic for evaluation of left knee pain and fever.  The knee pain began 2 months ago.  At the time of onset, the patient and several other children at day care had cough and rhinorrhea, but only the patient developed joint pain.  Movement is limited by pain in the morning but seems to improve in the afternoon.  For the past month, she has had a daily fever and an erythematous macular rash over her chest around bedtime.  Temperature is 36.1 C (97 F), blood pressure is 90/60 mm Hg, and pulse is 114/min.  Physical examination shows swelling, erythema, and warmth of the left knee, with pain elicited on passive and active movement of the left hip.  The patient can walk but has a slight limp.  Laboratory results are as follows:  Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

11ec25c8_d2ba_62de_bc81_49aae922a3dd_MD0003_00 This patient has chronic arthritis, daily fever, and a rash, which are consistent with systemic juvenile idiopathic arthritis (JIA). Systemic JIA is an arthritic autoinflammatory disease of childhood. The condition is characterized by ≥2 weeks of daily fever (quotidian fever), fixed arthritis lasting ≥6 weeks, and a pink macular rash that worsens during fever. As with other rheumatologic disorders, the joint pain and stiffness are classically worse in the morning and improve throughout the day. Other clinical findings may include lymphadenopathy and hepatosplenomegaly. The clinical presentation of systemic JIA differs from that of polyarticular or oligoarticular JIA, neither of which is associated with fever or rash. Characteristic laboratory findings of systemic JIA include leukocytosis, thrombocytosis, and markedly elevated inflammatory markers (eg, erythrocyte sedimentation rate, C-reactive protein) as well as anemia from chronic inflammation and/or iron deficiency. Treatment includes anti-inflammatory therapies such as nonsteroidal anti-inflammatory drugs and biologic agents. (Choice A) Acute lymphoblastic leukemia and other malignancies can present with fever as well as joint pain that is typically severe and may migrate. Cytopenia (eg, thrombocytopenia) should raise concern for malignancy. (Choice B) Although acute rheumatic fever can cause arthritis and rash, the pain of this type of arthritis is typically transient and migratory, as opposed to the fixed pain seen in JIA. In addition, this patient has no evidence of a preceding group A Streptococcus infection. (Choices C and D) Osteomyelitis is a hematogenous bacterial infection of the bone, not the joint space. Septic arthritis, a bacterial joint infection, is an orthopedic emergency that presents acutely with persistent fever, inability to bear weight, and progressive joint pain and swelling. This patient's intermittent fever, ability to bear weight, and chronic time course without symptom progression make infection unlikely. (Choice F) Transient synovitis typically presents in young children with acute pain and restricted range of motion of the hip joint following a viral illness. Fever is typically absent or low-grade, rash is uncommon, and inflammatory markers are normal or only mildly elevated. Educational objective: Systemic juvenile idiopathic arthritis is characterized by quotidian fever for ≥2 weeks, fixed arthritis for ≥6 weeks, and a pink macular rash that worsens during fever. Laboratory evaluation typically reveals leukocytosis, thrombocytosis, elevated inflammatory markers, and anemia. References: The child with joint pain in primary care. (http://www.ncbi.nlm.nih.gov/pubmed/26096092) Systemic juvenile idiopathic arthritis: diagnosis and management. (http://www.ncbi.nlm.nih.gov/pubmed/26916892)

A 2-Year-Old Girl Is Brought to the Clinic for Evaluation