creation date: 2026-02-05 21:12
tags: Pathologies Incomplete
Psoriatic Arthritis
Background
Definitions
Psoriatic arthritis (PsA) is an inflammatory MSK disease associated with psoriasis.
PsA was previously considered a variant of rheumatoid arthritis but is considered a distinct condition (typically seronegative).
Etiology and Pathogenesis
The development of psoriasis and psoriatic arthritis are not well understood but it is generally agreed upon that there is great complexity and heterogeneity in pathogenesis.
Genetic factors
A number of genetic findings have supported heritability of psoriatic arthritis. A number of genes relating to MHC complex and psoriasis have effect on predisposition of psoriatic arthritis.
Environmental and other factors
A number of non-genetic factors are implicated in the development of PsA:
- Obesity (for psoriasis)
- Psoriasis (nail, scalp)
- Streptococcal infection
- Altered gut and skin microbiome
- Trauma (Koebner phenomenon)
Pathology
Environmental triggers on a genetically predisposed patient results in chronic inflammatory response involving the joints and skin. Cytokines and interleukins result in inflammation of the periarticular space and tissue.
As infection or mechanical stress is often the inciting event, involvement may be asymmetric and affect fewer joints than more systemic inflammatory arthritis.