Crowned Dens Syndrome Mimicking Septic Arthritis in a Renal Transplant Recipient

Crowned dens syndrome (CDS) is a rare manifestation of calcium pyrophosphate deposition (CPPD) disease, characterized by crystal deposition surrounding the odontoid process. It typically presents with acute neck pain, restricted cervical movement, and elevated inflammatory markers, frequently mimicking infection or other inflammatory conditions. We report a 66-year-old man with end-stage renal disease secondary to congenital obstructive uropathy and a cadaveric renal transplant, maintained on tacrolimus and prednisolone. He presented with worsening left wrist pain and swelling accompanied by severe neck pain and marked restriction of cervical movement. Elevated inflammatory markers and peripheral joint inflammation initially raised concern for septic arthritis, prompting joint aspiration and empirical intravenous antibiotics. Persistent neck pain led to computed tomography (CT) of the cervical spine, which demonstrated characteristic peri-odontoid calcification consistent with CDS. Magnetic resonance imaging (MRI) demonstrated mild thickening of the cruciate ligaments and excluded cervical cord compression. Radiographs of the left hand and wrist demonstrated soft-tissue calcification consistent with peripheral CPPD. Following multidisciplinary rheumatology and nephrology input, he was treated with colchicine and an increased corticosteroid dose, resulting in rapid clinical improvement and near-complete resolution of symptoms. This case demonstrates an important diagnostic challenge in renal transplant recipients. Chronic immunosuppression increases susceptibility to infection, making prompt exclusion of septic arthritis essential in patients presenting with an acutely swollen joint. However, chronic kidney disease and associated abnormalities of mineral metabolism also predispose to CPPD. CDS should therefore remain an important differential diagnosis when significant neck pain and restriction persist despite initial treatment. CT is particularly valuable for demonstrating characteristic peri-odontoid calcification, while MRI provides complementary assessment when neurological or alternative spinal pathology is suspected. Renal transplantation should not narrow the differential diagnosis to infection alone. CDS should be considered in patients with persistent acute neck pain and risk factors for CPPD once serious infection has been appropriately investigated. Early CT imaging and multidisciplinary management can facilitate diagnosis, enable appropriately tailored anti-inflammatory therapy, and avoid unnecessary prolonged antimicrobial treatment or invasive investigation.