Abstract
Infectious sacroiliitis is a rare and challenging diagnosis. Sacroiliac joint changes related to pregnancy and puerperium can predispose to this condition. However, its clinical presentation can often mimic common causes of lower back pain and delay the diagnosis. We report the case of a 31-year-old pregnant woman with twins who presented at 29 weeks of gestation with lower back and right buttock pain that radiated down to the thigh. Although initially interpreted as sciatica pain, the diagnosis of psoas hematoma complicated with infectious sacroiliitis was made. With this case, we aim to bring awareness to this condition in order to raise suspicion among clinicians for an earlier diagnosis.