We presented a 5-year-old boy with fever, limping, and hip pain for six days. There was no abnormal past medical history. He kept his left leg immobile and slightly flexed, and externally rotated in the hip joint. Laboratory findings showed leukocytosis and elevated ESR and CRP. Hip sonography was normal. Hip magnetic resonance imaging (MRI) found no joint effusion but elucidated signs of inflammation in muscles of the periarticular and proximal femoral area (iliopsoas and gluteus maximus), and no collection could be noticed. We provided a thorough discussion on differential diagnoses and approaches to the patient.

This study reports a 43 years-old man diagnosed with piriformis Pyomyositis. A literature review was conducted by searching MEDLINE via Pubmed for English language case reports, published from 8th December 2019 to 20th January 2020. Patients' symptoms, laboratory tests, imaging, treatment, and other comorbidities were evaluated. Thirty-two cases diagnosed with piriformis Pyomyositis, of which 21 patients developed piriformis abscess (including one new patient added by us) of which 52. 4% were female, and the mean age was 26. 98 ± 17. 5. The most common manifestations were fever, lower back pain, and limited ambulation with increased ESR, CRP, or leukocytosis. Staphylococcus aureus was the most prevalent (57. 14%) pathogen isolated. The authors suggested gynecologic manipulations, muscle overuse, and other co-infections as probable risk factors. However, we fail to find any association between these factors and abscess formation (p>0. 05). Piriformis abscess should be regarded as a probable diagnosis in patients with gluteal pain, fever, and limited ambulation that have raised inflammatory markers or leukocytosis. MRI and CT scans are beneficial in diagnosing Pyomyositis in early-stage. Full recovery is expected with timely antibiotic and surgical treatments.

Soft tissue infections occur in any age with many risk factors such as age, immunosuppression, drug abuse, connective tissue and systemic diseases, obesity, trauma, burns, surgery, alcoholism and malnutrition.Soft tissue infections are classifiedassuperficial (cellulitis, superficialfasciitis, infectivebursitisortenosynovitis) and deep (deep fasciitis, Pyomyositis and infected myonecrosis) both of which could be diffuse or progress to phlegmon or abscess formation.1 There are different imaging modalities for diagnosis, but MRI is the modality of choice for the evaluation of the extent of soft tissue infections.Pyogenic infection of muscle is termed Pyomyositis, which frequently leads to abscess formation. A healthy muscle is usually resistant to the infection process of systemic disease, but connective tissue disorders, immunosupression, diabetes mellitus and trauma may be the underlying conditions.