Rethinking Limp Diagnosis: Brodie's Abscess Linked to Streptococcal Infections

BACKGROUND Brodie's abscess is a subacute osteomyelitis, most often seen in the long bones of children. In the emergency department (ED) these patients usually present with prolonged atraumatic limb pain and no signs of systemic infection. There is usually no known triggering factor for this infection. We describe a case of Group A Streptococcus (GAS) pharyngitis resulting in Brodie's abscess, which has not been reported previously. CASE REPORT A 6-year-old boy with 4 days of sore throat presented to his pediatrician and was treated with amoxicillin for a confirmed GAS pharyngitis. He presented to the ED on day 6 with fever, atraumatic left knee pain, swelling, and decreased range of motion (ROM) and was admitted after a workup suggested septic arthritis. MRI identified Brodie's abscess of his distal femur. Wound cultures grew Streptococcus pyogenes (GAS). Following a 4-day hospitalization with IV clindamycin, he was transitioned to cephalexin and discharged. On day 22, he returned with knee pain, swelling, warmth, and decreased ROM. Repeat MRI showed recurrent subperiosteal abscess and osteomyelitis of the femur with Brodie's abscess. After a course of IV clindamycin and 2 surgical debridements, he was discharged with complete resolution at 2-month follow-up. This Brodie's abscess case was attributed to a recent streptococcal pharyngitis, highlighting the importance of history taking, a high index of suspicion, and complications of streptococcal infections. CONCLUSIONS Physicians are taught that a child with a limp needs an X-ray to rule out a fracture, and if the X-rays are negative, an arthrocentesis to rule out a septic joint. Due to the increased incidence of more invasive streptococcal strains, MRI imaging may be needed to rule out Brodie's abscess in children, especially those with recent streptococcal infections.