Dactylitis represents a unique and diagnostically important manifestation of pSpA, with the following significant clinical implications:
• Dactylitis (“sausage digit”) refers to diffuse swelling of an entire finger or toe and is considered a hallmark feature of pSpA, especially PsA, but also occurs in other SpA subtypes.
• Its presence is strongly correlated with peripheral arthritis, often co- occurring and signifying increased disease activity and severity.
• Patients with dactylitis demonstrate higher disease burden, including increased joint inflammation (higher swollen and tender joint counts), elevated CRP, and more frequent ultrasound-detected synovitis and bone erosions, even early in the disease course.
• Dactylitis is also linked to extra-articular features. Its presence increases the risk for uveitis and IBD, making it a useful marker for identifying patients with potentially more complex or systemic involvement.
Role in differential diagnosis
• Dactylitis is a major criterion in the ASAS classification for pSpA, helping differentiate SpA from other forms of arthritis such as RA or osteoarthritis, where dactylitis is rare.
• It is highly characteristic of PsA, but can also be seen in other forms such as enteropathic arthritis and, less commonly, in ReA.
• Its recognition in a patient with suggestive musculoskeletal symptoms can prompt earlier diagnosis and appropriate risk stratification for more aggressive or multisystem disease.
REFERENCE
1. Kenyon M, Gallagher P, Dinneen B, O’Shea F, McManus R. Distinct clinical outcomes linked to peripheral arthritis and dactylitis in axial spondyloarthritis: findings from a retrospective Irish cohort. Rheumatol Int. 2024 Nov;44(11):2517-2525.
2. Carron P, De Craemer AS, Van den Bosch F. Peripheral spondyloarthritis: a neglected entity-state of the art. RMD Open. 2020 May;6(1):e001136.
3. Hamard A, Burns R, Miquel A, Sverzut JM, Chicheportiche V, Wybier M, et al. Dactylitis: A pictorial review of key symptoms. Diagnostic and Interventional Imaging. 2020 Apr 1;101(4):193–207.