A case of psoriasis vulgaris with diffuse idiopathic skeletal hyperostosis involved with ossifications of posterior and anterior longitudinal ligament.

Diffuse idiopathic skeletal hyperostosis (DISH) is difficult to distinguish from various forms of inflammatory arthritis, including psoriatic arthritis (PsA), rheumatoid arthritis, and ankylosing spondylitis. A 67-year-old Japanese male had been treated for psoriasis vulgaris for 13 years. Numbness of his right arm and lower limbs and spinal stiffening had developed 7 years prior to his initial evaluation at our facility. He noticed pain mainly while exercising. There were symmetrical marginal syndesmophytes in the spine, from the thoracic vertebrae to the upper lumbar vertebrae, on radiological examinations. We therefore suspected DISH. Furthermore, ossifications of the posterior and anterior longitudinal ligaments were noted in the cervical spine. Laboratory examinations revealed a normal peripheral white blood cell count, serum C-reactive protein, and erythrocyte sedimentation rate, and he was negative for rheumatoid factor. We detected human leukocyte antigen B39 but not B27. All distal interphalangeal joints were swollen but without pain. X-ray imaging showed narrowing of the joint space, and the consolidation of the joint was recognized, but there was no new juxta-articular bone formation. Based on clinical and radiological findings, we concluded that he had DISH and not PsA. DISH was indicated by marked radiological features of the axial skeleton, particularly the thoracic spine, but may also have involved the peripheral joints. DISH is one of the entheseal disorders, and 10% of Japanese middle-aged and elderly men have DISH. Therefore, the differentiation of DISH from PsA is necessary in psoriasis patients with spinal involvement.