A 10-year-old child presented with a 7-day history of progressively increasing pain of insidious onset in the lower back radiating to the right hip, aggravating during night which was associated with high-grade fever and constitutional symptoms. There was an associated limp, present since the onset of pain with restriction of floor level activities. The patient was able to perform his activities of daily living before the onset of symptoms. There was no history of trauma nor any close contact with any tuberculosis patient in recent months. On general examination, no grossly evident swellings or any foci of infection were present. The gait of the child was markedly normal. Tenderness at L3, L4, and L5 level was noted with no other significant findings in the spine. Neurological status of both lower limbs was normal. A fixed flexion deformity of 20  of the right hip was present with further flexion up to 100 . Range of motion in other planes was normal in the hip joint. The movements in the right hip were associated with discomfort but not outright pain. A clinical diagnosis of an infective etiology of either hip or spine was made.
The total white blood cell (WBC) count was 23,100 cells/mm3 (4000-11,000), erythrocyte sedimentation rate (ESR) 20 mm/h (up to 10 mm/h), and high-sensitivity C-reactive protein (hS-CRP) was 146.25 mg/dl (<2 mg/dl) at presentation. Ultrasonography (USG) of bilateral hip joints and abdomen showed mild effusion in the right hip with the left hip being normal and a well-defined hypoechoic area measuring 3.3*4.4*5.2 cm in the right psoas without any mobile internal contents. To further delineate the extent of abscess and the health and status of the spinal cord, magnetic resonance imaging (MRI) of lumbosacral spine was done which showed a large collection of dimensions 11.2*2.3*2.5 cm, hypointense on T1W images and hyperintense on T2W and short-tau inversion recovery (STIR) sequences were noted in the right psoas muscle, extending from the L2 vertebral body up to iliopsoas complex and further extending to the level of coccyx (Fig. 1). There was an extension of the swelling into the anterior epidural space through the right neural foramina at the level of L4-L5 vertebral body without any significant cord compression or myelopathy. L4 vertebral body and posterior elements were showing hypointensity on T1W and hyperintensity on T2W and STIR sequences. Samples were sent for blood culture and sensitivity before initiating the patient on empirical antibiotics, which came out to be positive for methicillin-sensitive Staphylococcus aureus (MSSA) sensitive to clindamycin, linezolid, tetracycline, and chloramphenicol. A trial of USG-guided aspiration of the psoas abscess was done, but the procedure was abandoned due to irritability of the child. A final diagnosis of pyogenic L4 vertebral body osteomyelitis with septicemia was made.
Initially, ceftriaxone and amikacin were started empirically. Later, clindamycin was started as a definite antibiotic after obtaining the blood culture report. The general health of the child as well as blood inflammatory markers started to improve gradually after the initiation of antibiotics (Table 1). A total of 2 weeks of intravenous antibiotics followed by further 4 weeks of oral antibiotics were advised. The patient started improving clinically with complete relief of pain by 2 weeks and the patient resuming his active schooling. Repeat MRI at 3 months showed complete resolution of the lesion in psoas as well as L4 vertebral body (Fig. 1). At 12-month follow-up, the patient has no symptomatology without any affection of any activities.