microRNA in Erosive Hand Osteoarthritis and Psoriatic Arthritis

Erosive osteoarthritis of the hand (EHOA) is a rare subset of HOA that affects mainly postmenopausal middle-aged women, featured by prominent signs of inflammation, severe progression, and typical radiographic changes of the interphalangeal (IP). It is presently debated whether EHOA is an advanced stage of the classical HOA or a separate entity with peculiar inflammatory features, which can mimic chronic arthritis such as psoriatic arthritis (PsA). PsA is a chronic immune-mediated inflammatory arthropathy, that affects 14.0-22.7% of patients with psoriasis. It is a highly heterogeneous disease, whose clinical features often vary from peripheral arthritis, to spinal spondylitis, and/or asymmetrical synovitis, enthesitis, dactylitis. As no gold-standard diagnostic test for PsA exists, the diagnosis is based on different patterns of clinical, radiological and serological markers included in the classification criteria for psoriatic arthritis (CASPAR). Some typical features of PsA are also observed in other chronic musculoskeletal diseases, as rheumatoid arthritis (RA) and HOA, determining possible delay of the diagnosis and consequent influence on the successful results of the therapies. In particular, the differential diagnosis of PsA and EHOA is very challenging, considering that both conditions can be characterized by bone proliferation and inflammation processes in the distal IP joints and lack of specific diagnostic biomarkers. In the last decade, microRNA (miRNA) are emerged as possible candidate biomarkers in different rheumatic diseases. They are a class of small non-coding RNA molecules implicated in the direct regulation of the expression of different target genes by repressing or inhibiting translation. Mature miRNA are produced inside the cell and exert their function in the cytoplasm, but also by being released into the circulation and body fluids, where they regulate both physiological and pathological processes. Specific profiles of miRNA have been asso