Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 13 2 2021 04 10 252 256 Mohammadreza Salehi Department of Infectious Diseases, Imam Khomeini ‎Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran Fereshteh Ghiasvand Department of Infectious Diseases and Liver Transplantation Research Center, Imam Khomeini ‎Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran Mohammad Mehdi Feizabadi Department of Microbiology, Thoracic Research Center, School of Medicine, Imam Khomeini ‎Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran Mohammad Zarei Joint Reconstruction Research Center, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran Niloofar Ayoobi Yazdi Department of Radiology, Advanced Diagnostic and Interventional Radiology Research Center, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Neda Alijani Department of Infectious Diseases, Shariati‎ Hospital, Tehran University of Medical Sciences, Tehran, Iran Mehdi Qaempanah Department of Medicine, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Simin Seyedpour Department of Medicine, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Research Center for Immunodeficiencies, Children’s Medical Center Hospital, Tehran University of Medical Sciences, Tehran, Iran 2020 09 17 2021 02 07 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. https://ijm.tums.ac.ir/index.php/ijm/article/view/2783 https://ijm.tums.ac.ir/index.php/ijm/article/download/2783/1341