Case Report: Diagnosis of Pediatric Osteomyelitis With Reduced Sensitivity of Inflammatory Markers

Researchers investigated the case of a 12-month-old boy who illustrated symptoms of Kingella kingae osteomyelitis. Results of the study were published in the American Journal of Emergency Medicine.

The boy presented to the emergency department with right heel pain and limping for 10 days. Prior to this, he had been diagnosed with cellulitis and received treatment with oral clindamycin and ibuprofen. The patient also had symptoms of an upper respiratory infection.

The patient’s vitals were within normal limits, although a musculoskeletal exam revealed “exquisite tenderness on compression of the right heel,” and a radiograph of the foot that was normal. However, the researchers noted that magnetic resonance imaging (MRI) was consistent with osteomyelitis; K kingae was indicated in an intraoperative bone culture. The patient was treated with intravenous cefazolin and washed out by orthopedics in the operating room. After a transition to oral amoxicillin therapy, the patient was sent home with no known complications.

“The most common presenting complaint of calcaneal osteomyelitis is a painful foot with a limp, progressing in severity to avoidance of walking,” the researchers noted, adding that these patients typically appear otherwise fine — sometimes presenting only with a “vague [upper respiratory infection] or diarrheal illness.”

They also noted that only 22% of pediatric patients with calcaneal osteomyelitis presented with a fever >38°C, and rarely was there a history of a preceding fall or injury.

Inflammatory markers, including erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), are highly sensitive laboratory findings in pediatric osteoarticular infections. For example, one large study found that both ESR and CRP were elevated in 94% and 95% of patients, respectively. Researchers of the study indicated that “ESR peaks at 3 days and remains elevated for up to 3 weeks, while CRP peaks at 2 days and returns to normal at 1 week.” 

However, despite the utility of these markers, the researchers indicated important limitations. The sensitivity of these inflammatory markers decreased with smaller bone infections such as calcaneal osteomyelitis. In addition, calcaneal osteomyelitis due to K kingae infection has been demonstrated to independently lead to reduced CRP sensitivity.

“This case highlights that prior antibiotic use and small bone location can diminish inflammatory marker sensitivity in the evaluation of pediatric osteoarticular infections,” the researchers concluded. “Despite normal ESR and CRP levels, a high clinical index of suspicion based on history and physical exam led to definitive imaging. [An] MRI serves as a highly sensitive imaging modality for osteoarticular infections in scenarios where diagnostic uncertainty exists.”

Reference

Ingersoll J, Halliday M, Adams DJ, Maj MC, Auten JD, Ponce DM. Inflammatory markers limitations in the diagnosis of pediatric calcaneal osteomyelitis [published online August 24, 2019]. Am J Emerg Med. doi:10.1016/j.ajem.2019.158416

This article originally appeared on Rheumatology Advisor