INTRODUCTION Iliopsoas abscess (IPA) is not a common disease in children and it is considered exceptional in neonates. First description of IPA was given by Mynter in 1881 and was called "psoitis". 1 Fewer than 30 cases of neonatal iliopsoas abscess have been reported in literature so far. 2 To the authors' knowledge, this is first case report from Pakistan. The authors present exceptional case of IPA in a 11-day old neonate who presented to us with complaints of reluctance to feed, swelling around left hip joint, crying while changing diaper and fever. IPA was diagnosed on ultrasonography and computed tomo- graphy. Incision and drainage of abscess was done and around 30 cc of pus was drained. The neonate was given intravenous antibiotics, according to culture and sensitivity, and was discharged when stable and tolerating oral feed. CASE REPORT A full-term female neonate with birth weight of 2.3 Kg was born by caesarean section due to maternal history of short pelvis. The pregnancy and post-natal period were uneventful and the neonate was discharged on full breast feed. On 11 th day of life, swelling was noted in the left hip region with excessive crying on changing diaper. She was brought to the pediatric emergency department on the next day with complain of fever and refusal to take feed .BCG vaccination was already given on the 3 rd day of life. The neonate did not receive any intra-muscular injection. There was no history of trauma or any insect bite on the affected thigh. On examination, she looked unwell and there was ill- defined swelling in left hip region extending upto the left flank, with bluish discoloration of the surrounding area (Figure 1). She had abduction deformity of left leg. There was limitation of range of motion. Oral thrush was also noted although the neonate was exclusively breast-fed. Laboratory investigations revealed haemoglobin of 10.3 gm/dL , WBC count of 42.9 x10 9 /L, platelet count of 825x10 9 , neutrophil count 73.8% and CRP was 96 g/L. Her serology tests were negative and blood culture was positive for pseudomonas aeruginosa. Chest X-ray and X-ray abdomen pelvis including hip joints were normal. Bone scan was also done and no bony pathology was noted. Ultrasonography revealed hypoechoic areas with thick internal echoes measuring approximately 14 ml involving left illiopsoas muscle extending into the gluteal region and proximal part of thigh suggestive of abscess formation. CT-scan pelvis with contrast showed left IPA extending from the level of iliac crest down to left thigh with few enlarged inguinal lymph nodes with surrounding soft tissue edema of upper thigh and buttocks (Figure 2). Journal of the College of Physicians and Surgeons Pakistan 2019, Vol. 29 (Special Supplement 1 of Case Reports): S45-S47 S45 CASE REPORT Primary Iliopsoas Abscess in a Neonate Muhammad Umar Nisar 1 , Samer Sikander 3 , Zenab Noorain 2 , Mehr-un-Nisa Shahid Baig 1 and Nadeem Akhtar 1 ABSTRACT Iliopsoas abscess (IPA) is rare in children but exceptional in neonates. Fewer than 30 cases have been reported in literature. We present a case of 11-day neonate who was brought with left inguinal swelling along with significantly raised white cell count and positive C-reactive protein (CRP). Ultrasound and CT scan confirmed the diagnosis of IPA. Drainage of abscess was done by open method through extraperitoneal approach. Systemic antibiotics, according to culture and sensitivity, were given and the neonate recovered well and was sent home. IPA can be primary or secondary. Primary IPA is more common in neonates unlike adults, who have secondary IPA in majority of the cases. Primary IPA spreads by hematogenous route from distant occult source in the body. Staphylococcus aureus is the causative organism in most cases of primary IPA. Septic arthritis of hip joint is among important differentials. Ultrasound and CT scan are helpful in diagnosis in the presence of raised white cell count and positive CRP. Drainage of pus by open method and through extraperitoneal approach is preferred method although ultrasound-guided percutaneous drainage has also been done with successful outcome. In conclusion, neonatal IPA is extremely rare entity and can easily be overlooked. High index of suspicion is required for its diagnosis in cases where a neonate presents with groin swelling, limited or painful motion of leg and fever. Key Words: Iliopsoas abscess, Neonate, Idiopathic, Pakistan. 1 Department of Paediatric Surgery / General Surgery 2 , The Children's Hospital, Pakistan Institute of Medical Sciences, Islamabad, Pakistan 3 Department of Paediatric Medicine, PAEC General Hospital, Islamabad, Pakistan Correspondence: Dr. Muhammad Umar Nisar, Department of Paediatric Surgery, The Children's Hospital, Pakistan Institute of Medical Sciences, Islamabad, Pakistan E-mail: dr.umarnisar@yahoo.com Received: November 14, 2018; Accepted: January 02, 2019