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Previously healthy 2-year-old presents with sore throat, limp
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A previously healthy 2-year-old female presented to the ER complaining of a 2-day history of a mild sore throat and limping on her right lower extremity; 2 weeks earlier, the patient had a mild upper respiratory tract infection. There was no history of injury, and her past medical history was unremarkable, with up-to-date immunizations. Her family and social history reveal no sick contacts, travel or exposure to animal or insect bites.
Examination at that time revealed a playful, well-appearing child with a normal exam and vital signs. Believing that the hip was likely the source of the limp, ultrasound and plain radiographs were obtained yet found to be normal; the patient was sent home with the diagnosis of toxic (postviral) synovitis.
Source: Brien JH
Two days later, she returned to her pediatrician with recurrence of her limping gait. Examination at that time confirmed the limp with a right knee effusion without erythema or warmth (Figure 1), and the patient was admitted for observation. Lab tests revealed a normal CBC and C-reactive protein but an erythrocyte sedimentation rate (ESR) of 58 mm per hour. Pending tests included a blood culture and screening Lyme titer. An ultrasound of the right knee confirmed the presence of an effusion, whereas a plain radiograph demonstrated some thickening of the synovial lining. Following an assessment by an orthopedic consult, the diagnosis was again transient synovitis, with no further evaluation indicated. The patient seemed to improve overnight and was discharged.
Several days later, she was clinically unchanged, but the laboratory called, reporting that the previous blood culture was growing a Gram-variable coccobacillus. The patient was readmitted with the diagnosis of septic arthritis. An MRI of the knee is shown in Figure 2.
What’s your diagnosis?
A. Transient synovitis with contaminated culture
B. Reactive arthritis
C. Lyme arthritis
D. Septic arthritis due to Kingella kingae
Case Discussion
The blood culture revealed penicillin-sensitive Kingella kingae, a slow-growing, fastidious Gram-variable or Gram-negative, oxidase-positive, short coccobacillus; a component of the normal oropharyngeal flora in children. Arthrocentesis of the right knee revealed an exudate, but the Gram stain and culture were negative. The MRI revealed a large effusion along with thickened synovium, consistent with septic arthritis, without osteomyelitis.
Even without pretreatment, septic joints are often culture-negative. In this case, there was nonetheless no question that the cause of the joint effusion was the Kingella recovered from the blood. The patient received 6 days of intravenous ceftriaxone, and with significant clinical improvement, she was discharged home to complete an additional 2 weeks of high-dose amoxicillin (90 mg/kg per day divided into three doses daily), with a good outcome.
Kingella kingae is now well recognized as a common cause of bone and joint infections in young children. Modern culture methods are good at recovering Kingella, and if fluid can be inoculated directly into a blood culture bottle, the chances of isolation of Kingella increases. Clinicians should suspect infection with K. kingae in young children with negative blood cultures and negative joint fluid cultures, especially in those with a subacute clinical presentation. Most Kingella isolates are susceptible to penicillins and cephalosporins.
Studies have suggested that K. kingae may be the most frequent cause of septic arthritis in children younger than 4 years. Fever is frequent, and most children appear only mildly ill. Clinical findings of Kingella are very similar to those of Lyme arthritis or transient (toxic) synovitis of the knee joint, visible swelling, mild warmth, and erythema of the skin over the knee. The blood leukocyte count and inflammatory markers are usually minimally elevated.
Transient (toxic) synovitis is a common, self-limiting cause of acute unilateral hip or knee pain in young children that usually lasts less than a week. It is thought to be a postviral, autoimmune inflammatory condition, based on molecular mimicry. Patients present with hip or knee pain, often with low-grade fever and a recent history of a viral URI or gastrointestinal infection. Examination reveals limitation of range of motion and resistance to weight bearing. The CBC reveals minimal elevation of WBCs and mild to moderate increase in the ESR or CRP. A small effusion may be seen on ultrasound, and management includes rest and non-steroidal anti-inflammatory medications.
Reactive arthritis, which has much overlap with transient synovitis, is characterized by a sterile arthritis that occurs following viral infections or certain bacterial infections such as group A streptococcus, Yersinia enterocolitica, Shigella, Salmonella, Campylobacter, Meningococcus and Chlamydia. Up to 90% of reactive arthritides are associated with a positive HLA-B27. Reactive arthritis is occasionally preceded or accompanied by erythema multiforme.
Episodic monoarticular arthritis, with a moderately swollen knee joint is a feature of the third (late) stage of Lyme disease. Signs and symptoms of Lyme arthritis closely resemble those of Kingella arthritis. Unlike Kingella arthritis, there may be spontaneous but temporary resolution of the knee swelling, which usually relapses after some interval. Diagnosis is made clinically and by positive antibody titers, verified by immunoblot assay (Western blot).
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- The guest columnists are all from the Department of Pediatrics at Inova Children’s Hospital in Falls Church, Va.: Riva Kamat, MD; Irina Remsburg, MD; and David Ascher, MD.
- James H. Brien, DO, is with the department of infectious diseases at McLane Children’s Hospital, Baylor Scott & White Health, Texas A&M College of Medicine in Temple, Texas. He also is a member of the Infectious Diseases in Children Editorial Board. Brien can be reached at: jhbrien@aol.com.
Disclosure: Brien reports no relevant financial disclosures.
In Memoriam: Dr. Richard Schwartz (1938 - 2017)
This column is a tribute to Richard H. (Dick) Schwartz, MD, who died earlier this year. With 43 years of practicing medicine, Dick was a remarkable pediatrician and recognized leader in practice-based research; a passion recognized when he received the AAP Practitioner Research Award in 1989.
As a member of the AAP Section on Administration and Practice Management Executive Committee, Section on Otolaryngology-Head and Neck Surgery, Subcommittee on Diagnosis and Management of Acute Otitis Media, and Task Force on Substance Abuse, Dick was one of those remarkable clinical physicians with great research talent, on whose shoulders many of us stand.
I saw Dick many times at the annual IDC New York meeting, and corresponded with him on numerous cases over the years. Infectious Diseases in Children has featured two of his cases in this column, one being last December, and another in June 2013; this month’s column is an updated and reformatted version of the earlier column.