Tropical pyomyosistis is an uncommon condition in the United Kingdom. Early diagnosis and appropriate treatment are crucial for a good outcome. We had seen 13 cases in our previously published series from 1998 to 2009. This is an update showing a significantly increased incidence from 2010 to 2016. A retrospective review of all cases of pelvic pyomyositis in our centre from January 2010 to April 2016 was undertaken from case notes and radiology reports. All children with clinical and radiographic evidence of pyomyositis were included. Since our previous publication we had changed our practice to get an MRI scan in all children who presented with a limp, fever and raised inflammatory markers, and had no effusion in the hip ultrasound scan. We identified 24 children with a mean age of 7 years (range, 1 week to 14 years). MSSA (Methicillin-Sensitive Staphylococcus aureus) was the most common cultured organism (n=8). Median hospital stay was 9 days (3 to 12). Obturator internus was the most common muscle affected. All patients had appropriate antibiotics with 2 patients requiring surgical drainage of abscesses. The majority of children (n=22) showed a complete recovery with antibiotics only. Incidence of pyomyositis has increased dramatically in our population and early diagnosis can result in a good outcome. We recommend MRI scan in all patients who present with a clinical picture of septic arthritis of the hip but with no effusion

We herein report a case of isolated hip pain in a four year old boy. The importance of this project is the unusual history, presentation, ultrasound, MRI and blood culture results and treatment, which lead to the diagnosis of adductor pyomyositis with a rare organism (Streptococcus Mitis) in a temperate country. The patient presented with a one day history of malaise, fever, left groin pain and inability to weight bear on the left leg. There was no history of any predisposing infections or recent travel. A working diagnosis of transient synovitis / septic arthritis of the hip was made on clinical examination. Plain radiograph and ultrasound of the hip was normal with no effusion. Two consecutive blood cultures suggested Streptococcus Mitis bacteriaemia and MRI scan confirmed pyomyositis of the left hip adductors that was too small to drain. Streptococcus Mitis is a normal commensal organism of the oral cavity however it can lead to opportunistic infections particularly endocarditis. Echocardiogram revealed no cardiac complications, in particular no endocarditic vegetation. Patient was treated with intravenous benzylpenicillin for a week followed by oral phenoxymethylpenicillin for a week. As it was a soft tissue infection, a short course of antibiotics was sufficient and he made a complete recovery. Adductor pyomyositis must be considered as a differential diagnosis in a child with unusual presentation of hip pain. When an ultrasound is normal, MRI scan is warranted to confirm diagnosis. Septic screen should include blood cultures. The commonest organisms are the Staphylococcus family. However if Streptococcus Mitis is isolated, cardiac sources of infection resulting in septic emboli must be investigated. Repeated MRI scans are required particularly if the patient does not respond to medical management