A 16-year-old previously healthy young man presented to the Pediatric Infectious Disease Clinic in September of 20151week after arriving in the United States from a refugee camp in Mozambique with a 3-month history of pain and swelling in the upper leg just below the knee. He had no fever noted, no erythema over the knee, and his symptoms had not changed appreciably since arrival in the United States. He had not received any antimicrobial therapy for this condition. His erythrocyte sedimentation rate (ESR) at presentation was 40 mm/h with a C-reactive protein (CRP) level of 0.9 g/dL and a leukocyte count of 6,900 cells/microL (50% polymorphonuclear cells, 37% lymphocytes, 11% monocytes, 1% eosinophils, and 1% basophils). On examination, his affected knee was slightly swollen with mild tenderness over the medial aspect. No discharge or erythema was noted. His range of motion for his knee was slightly decreased for flexion and extension, and an antalgic gait was present. At that time, a plain radiograph demonstrated concerns of chronic osteomyelitis of the right proximal tibia although tumor or subacute fracture was also considered (Fig. 1). Contrasted magnetic resonance imaging (MRI)demonstrated findings consistent with chronic osteomyelitis along the medial aspect of the proximal tibial epiphysis and metaphysis, however, with a cloaca extending from a cortical disruption of the posteromedial tibial metaphyseal cortex (Fig. 2). Given a desire to pursue potential debridement and obtain cultures simultaneously, he underwent surgical debridement of the area the following day, cultures from which were sterile. Given his recent exposure to a refugee camp in Africa, the resulting potential for infection with an unusual organism was also felt to justify the need for an open biopsy with cultures. A cortical window was not created although extensive debridement of the area was performed. The joint space was not entered during the surgery. No orthopedic hardware or antimicrobial-impregnated beads were placed. Post-operatively, his wound healed well, with resolution of a serous drainage after several days. Given a non-reactive QuantiFERON gold assay for Mycobacterium tuberculosis and the frequency with which Staphylococcus aureus is implicated in osteoarticular infections in otherwise healthy children, we pursued empiric therapy for methicillin-susceptible S. aureus with nafcillin (chosed for its potent activity against this pathogen and ability to administer as a continuous infusion at home).He demonstrated marked improvement after completing 6 weeks of parenteral therapy, and his ESR and CRP normalized approximately 8 weeks into treatment. Per our local practice guidelines, he completed 6 months of total therapy with cephalexin in April of 2016. Given involvement of the growth plate with his infection, follow-up imaging was obtained 10 months post-operatively, which revealed a 1.3 cm leg length discrepancy (right leg shorter than his left). He was seen again in the infectious disease clinic 3 months after antibiotic completion and was back to his normal baseline, with plain radiographs demonstrating no concerns of recrudescent disease. A follow-up MRI was not obtained. He played a season of varsity soccer for his local high school that fall without incident.
In April of 2017, approximately 1 year after completing therapy, he was seen in the infectious disease clinic again. At that time, the patient reported a 7-day history of pain, redness, and swelling along the inner aspect of the right upper leg below his knee overlying his prior surgical site. However, his father reported that he had complained of these findings for several months. A firm, tender erythematous mass over the medial aspect of the proximal tibia was noted on examination, underlying his surgical scar, although no drainage was present and the range of motion of his knee was normal. He had been a febrile and denied any recent trauma to the area. His ESR and CRP were normal at this time, as was his total leukocyte count and his differential leukocyte count. Plain radiographs demonstrated concern of recrudescent chronic osteomyelitis in the proximal tibia, with worsening sclerotic changes compared with his most recent radiograph (Fig. 3). A contrasted MRI demonstrated abnormal signal intensity in the proximal tibial metaphysis and epiphysis, with an abscess connected to a nidus of presumed chronic osteomyelitis througha fistula tract running inferior to the physis (Fig. 4 and 5). He was taken to the operating room shortly after this, where an abscess eroding through to the posterior aspect of the proximal tibia was noted. The superficial portion of the abscess was drained, with drilling through the affected bone into the posterior aspect of the tibia followed by curettage of the entire area. A cortical window was not created nor was periosteal elevation noted. His post-operative wound healing was uneventful. Operative cultures produced monomicrobial growth of P.aeruginosa, which, given the heavy growth in the primary streaks on the agar plate, was not felt to be a contaminant. This isolate demonstrated intermediate resistance to piperacillin-tazobactam (minimum inhibitory concentration (MIC)=32/4 mg/L), resistance to gentamicin (MIC>2 mg/L), aztreonam (MIC>16 mg/L), and ciprofloxacin (MIC>2 mg/L).The isolate was susceptible to meropenem (MIC of 1 mg/L), cefepime (MIC of 8 mg/L), ceftolozane and tazobactam (MIC=1.5 mg/L), and ceftazidime (MIC of 4 mg/L).Cefepime and ceftazidime MICs were confirmed with E-testing.Noimprovement was seen after 72 h of empiric cefazolin, but he did improve following transition to meropenem. Immunological evaluation revealed normal levels of natural killer cells, immunoglobulins (IgG, IgA, IgM, and IgE), tetanus, and pneumococcal antibodies. A lymphocyte subset panel was normal. He also demonstrated a normal lymphocyte proliferation response to phytohemagglutinin and pokeweed mitogen and a non-reactive serology to human immunodeficiency virus.Given the absence of an oral treatment option, he was treated initially with several days of cefepime, followed by 49 days of meropenem. He was then transitioned back to cefepime for 14 days followed by 56 days of ceftazidime. A contrasted MRI performed 7 weeks and plain radiographs performed 3 months into treatment demonstrated no recrudescence of disease (Fig. 6). He maintained normal inflammatory markers during treatment. At the end of 4 months of therapy, his physical examination was normal and his antibiotic therapy was discontinued. He denied any persistent symptomatology and was participating in soccer again without difficulty.