Tophaceous pseudogout is characterized by deposition of calcium pyrophosphate dihydrate (CPPD) crystals within soft tissue. The condition, which was first described in 1962, appears radiographically as chondrocalcinosis involving hyaline and fibrocartilage (5). Tophaceous pseudogout is most commonly sporadic and shows an association with a variety of conditions, such as prior surgery, trauma, gout, hyperparathyroidism, hypophosphatasia, hypomagnesemia, hemochromatosis, and Wilson' disease (3). The appendicular skeleton is most commonly affected, and involvement of the spine is relatively rare in comparison. The proposed mechanism of disease in the spine consists of nodular deposition of CPPD crystals in the ligamentum flavum or atlanto-occipital ligament, with ensuing myelopathy or cervicomedullary compression (1, 2, 7). The cervical spine is most commonly affected and the thoracic spine is least affected (5, 6). Because the presenting symptoms mimic more common conditions such as spinal stenosis, lumbar radiculopathy, spondylolisthesis, or cauda equina syndrome, tophaceous pseudogout is not usually considered at presentation (4, 6). The diagnosis is made by examining the tissue under polarizable light and demonstrating positive birefringence.
In the case of our patient, risk factors included age and remote history of laminectomy for spinal stenosis. The diagnosis was not considered at presentation and was established after histologic examination of the tissue under polarizable light. This case demonstrates involvement of the lumbar spine by tophaceous pseudogout.
Contributed by Gerald F. Reis MD, PhD, Arie Perry MD