Case Presentation: A 9 month old boy was brought to the emergency department for two day history of right arm edema and refusal to move his right arm. He began having rhinorrhea and cough earlier in the week then developed non-bloody diarrhea. During that time period he had fevers up to 102.5 that responded to Tylenol. There was no trauma to the area and no history of autoimmune disorders. Patient was born at term, growth and development had been appropriate, but he was under vaccinated. On presentation at the emergency department, patient was febrile to 100.4, tachycardic to 188, and blood pressure of 115/94. Physical examination revealed erythema and edema of the right hand with erythema extending to the right distal forearm. There was hesitancy to move the fingers of his right hand. Edema was also noted of the right thigh. No erythema of the right thigh however it was warm to touch. Even though multiple attempts were made to have him stand he refused.Initial labs showed white blood count of 21.68, hemoglobin of 9.9, platelet count of 494, c-reactive protein of 53.5, procalcitonin of 0.25, ESR of >111, prothrombin time of 17, and PTT of 63. Comprehensive metabolic panel, urinalysis, lactate dehydrogenase, creatinine kinase, and lipase were normal. Blood culture showed no growth. COVID PCR on admission was positive. With the labs findings above being suspicious for septic joint, Orthopedics Surgery was consulted, however hip ultrasound did not show an effusion to drain. Patient was then admitted for further workup and possible MRI. MRI of the entire right lower extremity was performed and specifically the MRI of the right knee was significant for epiphyseal osteomyelitis/chondritis, metaphyseal osteomyelitis and intramuscular abscess in the lateral gastrocnemius Due to proximity to the growth plate, core needle biopsy of the surrounding tissue was obtained and culture was positive for Group A Streptococcus. Patient was discharged with long-term antibiotics and close follow-up with Infectious Disease.
Discussion: Acute osteomyelitis is an infection to the bone that can enter the bone hematogenously, by direct inoculation, or local invasion from an infection. In the pediatric population, every year, the incidence is from 1 to 13 cases per 100,000. This case describes an uncommon presentation of osteomyelitis emphasizing the importance of considering this diagnosis even when there are no focal signs and symptoms of inflammation. Acute osteomyelitis typically involves only one site, but this patient presented with multifocal acute osteomyelitis.This patient who presented with multifocal edema and inability to bear weight, the differential diagnosis was of many. It was important to not only include nonaccidental trauma, angioedema, serum sickness, mast cell activation, autoimmune conditions, incomplete Kawasaki, and a sequela of COVID, but also osteomyelitis. In this case with multiple causes being considered and inflammatory markers continued to downtrend while in the hospital, an extensive workup was performed before an MRI was obtained. Keeping osteomyelitis on the differential when there is multifocal involvement is crucial to preventing complications, such as recurrent infection, pathologic fractures, long-term functional impairment, and death.
Conclusions: Acute osteomyelitis can rarely present as a multifocal infection. Given the dire consequences of missing acute osteomyelitis, it is important that hospitalists recognize unusual presentations of osteomyelitis.