Retroperitoneal and iliopsoas abscess as Crohn's disease onset mimicking a common lumbosciatic pain.

Crohn's Disease (CD) refers to a chronic transmural bowel inflammation affecting a range between 5 and 15 per 100,000 person-years worldwide 1. In patients with stricturing CD, the transmural pattern of inflammation may trigger the development of sinus tracts able to connect to other tissues, leading to the formation of fistulas or abscesses 2. Intra-psoas abscesses are rare, affecting between 0.4-4.3% of patients with CD 3. We present the case of a 36-year-old male with no past medical history except for a two-week worsening lumbosciatalgia not responding to standard nonsteroidal anti-inflammatory drugs, who complained sudden abdominal pain, with right lower abdominal stiffness combined to a severe edema and erythema of the right lower limb, extended from the gluteus down to the knee, involving the anteromedial and posteromedial areas of his thigh. Patient was septic and CT scans revealed a large complex air-fluid collection within the right iliac region, involving terminal ileum, right retroperitoneum and right lateral abdominal wall towards the inner edge of his thigh. Diagnosis of CD was made on histopathology and the patient gained full recovery thanks to a prompt surgical intervention followed by high-dose antibiotic infusion and vacuum-assisted wound closure. Intra-psoas abscesses, albeit rare, are a known manifestation of CD and frequently lead to misdiagnosis because of their rarity and their unusual location easily mimicking other diseases. Therefore, clinician's awareness must be heightened for complicated CD in the setting of intra-psoas abscesses in order to avoid delayed treatment. KEY WORDS: Crohn disease, Psoas abscess, Sciatica, Late onset disorders, Negative pressure Wound therapy.