New developments in magnetic resonance imaging of the nail unit.

The evolution of dedicated magnetic resonance imaging (MRI) musculoskeletal equipment allows new sequences and better images of the nail unit. The use of MRI has modified the imaging strategies used in treating inflammatory arthritis. In the case of psoriatic arthritis (PsA), the MRI study of the nail unit identifies nail involvement, which appears as an initial lesion for the induction of distal phalanx damage and consequently of distal interphalangeal joint arthritis. All patients with psoriasis, even in the absence of a clinically evident onychopathy, show characteristic MRI changes in the nail. This evidence could have a practical diagnostic value, because MRI study of the nail could document diagnosis in patients with undifferentiated spondyloarthropathies who have a barely evident psoriasis. We discuss the advantages and problems related to the use of low-field and high-field MRI in the study of the nail unit of patients with PsA.