Differential diagnosis of pseudogout of the lumbar spine

This case report details a rare instance of calcium pyrophosphate dihydrate crystal deposition disease (CPPD), commonly known as pseudogout, affecting the lumbar spine. A man in his mid-50s of age presented with severe low-back pain and fever, initially suspected as a spinal infection. Elevated erythrocyte sedimentation rate and leucocytosis were observed, while the initial imaging showed only lumbar spondylosis with arthritic changes in the right L4–L5 facet joint. However, an MRI revealed a cystic lesion at the right L5–S1 facet joint without signs of spondylodiscitis. Ultrasound-guided needle aspiration and synovial fluid analysis, including polarised light microscopy, identified calcium pyrophosphate crystals. Treatment with intravenous pain management was initially ineffective. Confirmation of CPPD led to successful treatment with oral colchicine, resulting in rapid pain alleviation and fever reduction. The patient reported significant improvement at a 2-week follow-up. This case emphasises the importance of thorough investigation in differentiating common symptoms and avoiding unnecessary treatments, highlighting the role of histological examination in diagnosing rare conditions like spinal CPPD.