Background Data: Calcium pyrophosphate dihydrate (CPPD) deposition disease is a metabolic disorder caused by the deposition of CPPD crystals in the articular or periarticular structures that leads to inflammation of the joints. Spine affection is rare. Purpose: To present a rare case of lumbar facet joint cyst caused by calcium pyrophosphate arthropathy. Study Design: A case report with a brief review of the literature. Patient and Methods: Seventy-three-year-old man, who underwent PLIF L5/S1 ten years ago, presented with right L4 nerve root compression symptoms that have started two months ago. Clinical examination revealed no motor function disturbance but hypoesthesia in the L4 dermatome. He has no history of crystal deposition disorder. The patient underwent decompression and fusion at this level. Results: The symptoms were completely resolved postoperatively and after one-year follow-up. Histopathological examination of the cyst revealed fibrous granulation tissue. Examination of the tissue under polarized light showed positively birefringent, short blunt crystals of calcium pyrophosphate dihydrate. Conclusion: Calcium pyrophosphate arthropathy, although rare, should be incorporated into the differential diagnosis of cystic lesions of the facet joints. (2020ESJ221)