The parents of twin infants brings one of them, Juliet, a 5-month-old female, to the clinic. The baby has a painful red spot on her right elbow and a fever of 100.5°F.
Juliet’s parents report that her bottle intake was moderately less than usual. The infant became very fussy when her mother tried to put her down, and she would not sleep in her crib. The infant was most content in her mother’s arms. One week prior, Juliet and her twin brother tested positive for influenza B infection. Both infants were treated with oseltamivir phosphate.
On examination, her pulse, respirations, and blood pressure were within normal limits; her tympanic temperature was 100.9°F. The infant was alert, albeit more quiet than usual, according to her mother. She did not appear toxic.
The erythematous macule measured 1.2 cm and was without increased warmth, edema, or pus. There was no pain to light touch. However, Juliet was noticeably uncomfortable with a more firm palpation of the distal humerus just above the annular lesion. The remainder of her physical examination was unremarkable.
Acute hematogenous osteomyelitis was suspected, and the infant was sent to a local facility for urgent initial workup.
Laboratory tests and imaging
A radiograph of the right elbow showed no acute process. Her C-reactive protein (CRP) level was within normal limits, at 3.10 mg/dL. Her erythrocyte sedimentation rate (ESR) was elevated, at 77 mm/h. Her leukocyte count was elevated, at 19.6. Results of her blood culture were pending. Juliet was promptly transferred to a nearby children’s hospital for admission, further evaluation, and treatment.
An ultrasound of the infant’s right elbow showed no joint effusion or extra-articular soft tissue fluid collection. Magnetic resonance imaging (MRI), performed under general anesthesia, demonstrated abnormal low T1-weighted and bright T2-weighted marrow signals within the distal right humerus metaphysis with periosteal reaction extending along the shaft of the humerus.