Diagnosing psoriatic arthritis: A case report and review highlighting the role of imaging despite normal C-reactive protein values

Abstract: Psoriatic arthritis (PsA) is an autoimmune disease characterized by the inflammation of the skin (psoriasis), entheses (enthesitis), and joints (arthritis). Although PsA is predominantly associated with peripheral arthritis and enthesitis, a subset of PsA patients have axial disease. Generally, nonspecific markers of active inflammation, such as elevated C-reactive protein (CRP) levels and erythrocyte sedimentation rate (ESR), are recommended as laboratory markers to promote the diagnosis and measure disease activity in PsA. However, CRP levels do not correlate strongly with disease activity in PsA. This may delay treatment in patients who have active disease despite normal CRP levels. This case report demonstrates how imaging can be crucial for diagnosing PsA in patients with normal CRP levels, challenging the traditional reliance on inflammatory markers.