Psoas abscess is uncommon in childhood. It has an insidious onset, and diagnosis and management may be delayed because of non-specific symptoms and signs. A 12-day-old male infant was referred to hospital with skin abscesses and fever. He was born at 39 weeks gestation as the first child of consanguineous parents. His birthweight was 2600 g and there was no history of premature rupture of membranes or maternal fever. His maternal uncle died at 20 days of age due to an unknown cause. On admission, he had a 3 ¥ 3 cm swelling on the medial side of his left ankle, a 0.5 ¥ 0.5 cm swelling on his left hand and a nodule on the lateral side of the left ankle. Laboratory findings were as follows: leukocyte count 26 900/ mm (62% neutrophils, 38% lymphocytes); C-reactive protein 31.3 mg/dL and erythrocyte sedimentation rate 85 mm/h. The abscesses were drained and vancomycin and ceftazidime were initiated. Culture was positive for methicillin-susceptible Staphylococcus aureus. On the seventh day of admission, fever of 38.5°C and swelling and hyperemia on the right groin appeared. On ultrasonography (US) 10–14 mm hypoechoic fluid was seen on the right side of the bladder. Tuberculin skin test, salmonella, brucella, and HIV were negative. Magnetic resonance imaging (MRI) of the abdomen showed an 38 ¥ 16 ¥ 14 mm abscess formation with ring enhancement on the right inguinal region. The patient underwent percutaneous drainage but the drainage material contained very few polymorphonuclear leukocytes without microbiological growth. Antibiotic treatment was continued and follow-up US showed complete resolution of the abscess. On immunological work up, serum immunoglobulins and lymphocyte subset analysis were in the normal range according to age (Table 1). Phagocytic cell functions were also normal on nitroblue-tetrazolium (NBT) slide test. Flow cytometry results were as follows: CD18, 16%; CD11a + CD18, 17%; CD11b + CD18, 3%; CD11c + CD18, 4%. Neutrophil function was determined as 1.89 oxidative explosion, 1.63 phagocytosis and 1.43 chemotaxis (normal, >1.5). Antibiotic prophylaxis was initiated and bone marrow transplantation was recommended. Diagnosis of psoas abscess is difficult in neonates because of the rarity of this disease and the difficulty in differentiating this from septic arthritis due to similar clinical findings. Good physical examination is critical for prompt diagnosis. US and computed tomography are the preferred radiological tests for diagnosis. Psoas abscess in children may be primary or, rarely, secondary to an underlying pathology of kidney, cecum, appendix, or terminal ileum on the right side and fever. Neonates and children may have an antecedent or contemporaneous distant cutaneous infection. The causes of psoas abscess have changed in the last decades. In recent years S. aureus has been reported as the causative agent in 80% of primary psoas abscesses. Early drainage with appropriate systemic antibiotic coverage is the ideal treatment. Drainage of the abscess may be done through US-guided percutaneous drainage or surgical drainage. After complete abscess drainage up to 2 weeks of broad spectrum antibiotic treatment should be started pending culture results. Predisposing conditions to primary psoas abscess development are reported to be HIV infection, diabetes, immunosuppression and renal failure. Based on flow cytometry, the present patient was diagnosed with leukocyte adhesion deficiency type 1 (LAD 1; mild type). In conclusion, immunodeficiency syndromes such as LAD should be investigated in newborns with psoas abscess. The present case is important to emphasize underlying factors in the pathogenesis of psoas abscess.