Piriformis syndrome as the only initial manifestation of septic sacroiliac osteomyelitis.

Piriformis syndrome refers to sciatica symptoms that do not originate from spinal root compression, but involve the overlying piriformis muscle. Diagnosis is clinical since there are no definitive tests to confirm the diagnosis. Piriformis syndrome is often misinterpreted as sciatica or other pains. Rarely, it could be one of the manifestations of pelvic osteomyelitis. Pelvic osteomyelitis is rare in adults, but it is associated with high morbidity and mortality. One of the severe complications is bacteraemia, which is life-threatening and may be associated with poor outcome. Acute pelvic osteomyelitis is often not initially diagnosed owing to its non-specific symptoms, including fever and severe but poorly localised pain, which may result in a delay of appropriate treatment. Thus, prompt diagnosis is crucial to the prognosis. Here, we report a patient suffering from acute pelvic osteomyelitis with piriformis syndrome as the only initial manifestation without fever. This unusual manifestation rendered prompt and correct diagnosis difficult. © Royal College of Physicians 2020. All rights reserved.