242 Case Report Primary Pyomyositis as Unusual Cause of Limp: Three Cases in Immunocompetent Children and Literature Review Livia Drovandi1 Sandra Trapani1 Simona Richichi1 Donatella Lasagni1 Massimo Resti1 1 Paediatric Unit, Department of Sciences of Health, Anna Meyer Address for correspondence Livia Drovandi, MD, Paediatric Unit, Children’s Hospital, Florence, Italy Department of Sciences of Health, Anna Meyer Children’s Hospital, Viale Pieraccini, 24, 50139 Florence, Italy J Pediatr Infect Dis 2018;13:242–246. (e-mail: [email protected]). Abstract Pyomyositis (PM) is an uncommon primary skeletal muscle infection caused mainly by Staphylococcus aureus that is characterized by single or multiple intramuscular abscess formation. In our ward, between 2013 and 2015, three children (two females and one male) aged from 2 to 12 years were diagnosed and treated for PM. Patients’ medical records and imaging studies were examined retrospectively. All patients, otherwise healthy, complained of limp, fever, and severe lower limb pain. Skin scratch lesions were detected in two cases; one of them showed an edematous appearance of the affected area. Multifocal bilateral abscesses of gemini and gastrocnemius were detected in the youngest patient; right obturator and iliac muscles were affected in the second patient; and right gluteus and pyriform muscles were involved in the third patient. All patients showed elevated acute phase reactants and had normal serum creatinine kinase levels. Blood cultures and polymerase chain reaction (PCR) investiga- tions were negative in all cases. Magnetic resonance imaging (MRI) findings included muscle enlargement, deep fascia, high signal in subcutaneous tissues, and postgado- linium abscess formation. No patient required surgical or percutaneous drainage. All Keywords three were treated conservatively with intravenous oxacillin, associated with ceftriax- ► pyomyositis one in the first patient and ceftazidime in the other two, followed by oral antibiotic ► children therapy for a period ranging from 5 to 6 weeks. Pyomyositis must be considered as an ► limp unusual cause of limp in children of all ages. When promptly diagnosed and adequately ► musculoskeletal treated, it has a favorable outcome without relapses or sequelae as occurred in all our Downloaded by: Karolinska Institutet. Copyrighted material. infection patients. Introduction mius, abdominal, and spinal muscles. Prompt diagnosis is difficult because of nonspecific clinical signs and the wide Pyomyositis (PM) is a primary infection of skeletal muscles range of differential diagnoses. Radiological evaluation by characterized by intramuscular abscesses due to hematogen- magnetic resonance imaging (MRI) is extremely useful; the ous spread from occult sources. The most common micro- gold standard for diagnosis is the culture of pus aspirated from organism implicated is Staphylococcus aureus. Trauma, the affected muscles, when possible. Treatment consists of malnutrition, and immunodeficiency may have important intravenous antibiotics and abscess drainage depending on its predisposing roles. Primary PM in immunocompetent children size and depth. When not properly treated, PM can progress to is uncommon in nontropical regions. The most commonly osteomyelitis and septic arthritis, and even to life-threatening involved muscles are quadriceps, gluteal, ileopsoas, gastrocne- septic shock. Between 2013and 2015, three children aged from received Copyright © 2018 by Georg Thieme DOI https://doi.org/ March 13, 2017 Verlag KG, Stuttgart · New York 10.1055/s-0037-1604036. accepted after revision ISSN 1305-7707. May 18, 2017 published online July 4, 2017 Primary Pyomyositis as Unusual Cause of Limp Drovandi et al. 243 2 to 12 years were diagnosed and treated in our ward for was increased up to 17.8 U/L (normal value <7.3 U/L). Group multifocal PM. Patients’ medical records and imaging studies A Streptococcus-induced myositis was excluded by low anti- were retrospectively examined. Pyomyositis involved bilater- streptolysin O (ASO) and anti-DNase B antibody titers. ally gastrocnemius, gemini, and tibialis muscles in the young- A blood sample tested negative for Streptococcus pneumo- est patient, iliac and iliopsoas muscles in the second patient, niae, Streptococcus pyogenes,andStaphylococcus aureus by and gluteus and pyriform muscles in the third complicated polymerase chain reaction (PCR). A stool sample tested with iliac osteomyelitis. None of them had trauma, underlying negative for enteroviruses, rotaviruses, and adenoviruses diseases, or immunodeficiency. by PCR. A pharyngeal swab tested for adenoviruses, influenza viruses, and coxsackieviruses by PCR was also negative. Case 1 Serodiagnostic tests for Salmonella and Brucella were also negative. A 2-year-old female patient presented with fever, lower limb Lower limb musculoskeletal ultrasound showed abnormal pain, and refusal to walk. Ibuprofen was administered without echotexture with multiple hypoechoic little focal ovular lesions any improvement. There was no history of trauma, skin in the gemini and anterior tibialis muscles. X-rays of the lower lesions, or overseas travel. Diffuse tenderness in the gastro- limbs and chest, abdomen ultrasound, and cardiac echocolor cnemius muscles, slight limp, and unwillingness to bear Doppler were normal. MRI showed multiple bilateral ovular weight were associated with hyperpyrexia. Hip ultrasound focal areas of low attenuation in both gastrocnemius muscles revealed distension of joint capsule and moderate synovial with smooth peripheral rim enhancement after contrast enlargement. Laboratory data showed mild leukocytosis administration. Postgadolinium scans demonstrated patholo- (white blood cell [WBC], 20,000/µL) and an elevated C-reactive gical enhancement of the gastrocnemius fascia; similar pro- protein (CRP, 6.31 mg/dL). The child was discharged with nounced areas were found in the posterior and medial thigh diagnosis of transient arthritis on nonsteroidal anti-inflam- muscles with subcentimetric lymph nodes in popliteal fossa matory drugs (NSAIDs) and antibiotic treatment. Two days (►Fig. 1a, b). Suspecting a musculoskeletal infection, empiric later, the fever and limb pain had worsened, and the child now antibiotic therapy with ceftriaxone and oxacillin was com- also had a mild sore throat, vomiting, and diarrhea; she re- menced. On the third day, the child became apyrexial, muscle presented to the emergency department. Due to the increased tenderness progressively decreased, and she could walk. Clin- leukocytosis (WBC, 42,280/µL) and CRP (19.2 mg/dL), she was ical healing was confirmed by normalization of hematological admitted to our ward. Blood cultures were negativefor aerobic, and radiological features. After 2 weeks of IV antibiotics, she anaerobic, and fungal agents. Severe tenderness was still was discharged with a 3-week course of oral therapy. Three present on palpation of both calves; active, but not passive, months later, the child appeared in good general health; movement elicited pain. extensive immunological evaluations were normal, including Initially, a slight improvement in acute phase reactants quantitative immunoglobulins, enumeration of T-lymphocyte (WBC, 31,310/µL; CRP, 17.6 mg/dL; erythrocyte sedimenta- subpopulations, total hemolytic complement levels, and leu- tion rate [ESR], 43 mm/h) was observed. Creatine phospho- kocytefunction by reductionof nitroblue tetrazolium (NBT). Six kinase (CPK), lactate dehydrogenase (LDH), uric acid, and months later, an MRI confirmed complete remission. At 1-year ferritin levels were within normal ranges; serum aldolase follow-up, the patient had not suffered any relapses or sequels. Downloaded by: Karolinska Institutet. Copyrighted material. Fig. 1 Sagittal (a)andcoronal(b) lower limbs magnetic resonance imaging (MRI) indicative of multiple bilateral abscesses in both gastrocnemius muscles with smooth peripheral rim enhancement after contrast administration. Postgadolinium scans demonstrated pathological enhancement of its fascia with subcentimetric lymph nodes in popliteal fossa. Journal of Pediatric Infectious Diseases Vol. 13 No. 3/2018 244 Primary Pyomyositis as Unusual Cause of Limp Drovandi et al. Case 2 (WBC, 20,270/L; N, 83%). Ultrasound examination revealed a gluteal abscess and plain X-ray confirmed soft tissue edema A 12-year-old male patient was admitted to a peripheral in the right buttock. On physical examination, the girl was hospital complaining of right leg and gluteal pain with limp febrile and there was flexed decubitus of the right leg while and functional deficiency. There was no history of trauma or of the upper gluteal region was hot and swollen. Leg extension travel abroad. He suffered from atopic dermatitis and had and internal rotation of the right hip were limited and scratch marks over the popliteal skin. Topical anti-inflamma- painful. Infected scratch marks were noted on the sacral tory drugs were applied without any improvement. region skin. Blood cultures and ASO titer were negative. After Laboratory data were normal while lumbosacral spine X-ray making a provisional diagnosis of acute musculoskeletal showed S1 vertebral schisis. Neurological pain was suspected infection, IV oxacillin and ceftazidime were started. An and the child was transferred to our emergency department. abdominal MRI scan confirmed a large abscess in the right He appeared pale and uncomfortable; he had a low-grade fever gluteus muscle extending along its fibers into its insertion and cutaneous oozing lesions