Lytic Bone Lesion by Brucella spp.: A Delayed Diagnosis
03 May 2017
14 September 2017
11 December 2017 (eFirst)
In August 2005, a 3-year-old boy presented with left knee pain, functional disability, and intermittent fever. Four weeks later, a left knee X-ray was normal, blood tests showed hemoglobin 9.9 g/dL, leukocytes 11,100/µL, platelets 678,000/µL, C-reactive protein 6.9 mg/dL, and erythrocyte sedimentation rate 21 mm/h. Arthrotomy revealed cloudy liquid with negative culture. Initial treatment was established with intravenous flucloxacillin 100 mg/kg/day for 12 days followed by oral flucloxacillin 60 mg/kg/day for 10 days.
After discharge and during the following 4 months, the patient was reassessed on eight occasions (three in the emergency department). He did not have fever again. A chronic arthritis making walking impossible during its worst phases, with intense pain but without inflammatory rhythm, led to a pediatric rheumatology review in January 2006.
Consultation of the clinical file by the pediatric rheumatology staff surprisingly revealed a positive blood culture for Brucella spp. (BD BACTEC Peds Plus/F Culture Vials–digested soya–casein liquid with resins for 30 days) performed 4 months earlier. Clinical examination showed left knee swelling, 30-degree knee flexion, a warm joint without erythema, and intense pain in any knee movement. The remaining physical examination was normal. Wright's reaction (1:1,280) and immunofluorescence for Brucella spp. (1:1,280) confirmed active infection. The X-ray revealed an epiphyseal lytic lesion (type V classification by Roberts and colleagues) on the left lateral condyle of the femur ([Fig. 1]). Bone scintigraphy was suggestive of osteomyelitis on the left lateral condyle of the femur. Treatment with intravenous gentamicin 5 mg/kg/day (7 days), oral trimethoprim–sulfamethoxazole (50 mg/kg/day of sulfamethoxazole), and oral rifampicin 20 mg/kg/day for 6 weeks was complicated by a Jarisch–Herxheimer reaction, as previously published in PIDJ (Pediatr Infect Dis J 2016; 35:466). The Wright's reaction titer fell to 1:160 in 2 weeks. A fully functional recovery was achieved 3 months later, without relapse. Left-knee X-ray performed 5 years later was normal ([Fig. 2]). The patient is now healthy and 14 years old.
In our hospital, all patients' information is digitally stored and available only since 2007. Previously, laboratory results were filed in different sections of the patient's file, which may justify the delay in knowing the result of blood culture.
The diagnosis was obvious at the first pediatric rheumatology observation. The finding of a lytic lesion on X-ray of the symptomatic knee suggested a Brucella spp. osteomyelitis complicated by bone reabsorption. The need for general anesthesia and the delay to perform magnetic resonance imaging in our hospital justified the option for radionuclide scan.
In children, common solitary lytic epiphyseal lesions of bone are often infectious subacute or chronic osteomyelitis (Staphylococcus aureus, Kingella kingae, Streptococcus pyogenes, Haemophilus influenzae, Pseudomonas, Mycobacterium tuberculosis, atypical mycobacteria, Bartonella henselae, Brucella spp.) or chronic nonbacterial osteomyelitis.   Other, uncommon causes of solitary lytic epiphyseal lesions are bone cysts, bone sarcoma, hydatid cyst, Langerhans cell histiocytosis, osteoid osteoma, and sarcoidosis.  
Osteoarticular manifestations of Brucella spp. infection in children are peripheral monoarthritis, mainly involving the hip or knee. In patients older than 15 years, sacroiliitis and spondylitis are the most frequent manifestations.  Osteomyelitis is very rare in children.  We did not find any pediatric case reports of Brucella spp. lytic lesions and only a few in adults.
In endemic regions, a lytic bone lesion must evoke brucellosis as a possible diagnosis.
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