<unk>  occurs mainly in people who have pre-existing psoriatic<unk> , but can occur, if less often, in advanced rheumatoid<unk> ; it can also occur independently. Psoriasis and psoriatic<unk>  are interrelated heritable diseases, occurring with greater heritable frequency than rheumatoid<unk> , primary Sjögren syndrome and thyroid disease. Psoriasis affects 2–3% of the Caucasian population, and psoriatic<unk>  affects up to 30% of those.<unk>  presents in about 5–16% of psoriatic<unk>  cases, involves osteolysis of the DIP and PIP joints, and can include bone edema, bone erosions, and new bone growth. Most often psoriatic<unk>  is seronegative for rheumatoid factor (occurring in only about 13% of cases), and has genetic risk factor overlap with ankylosing spondylitis with HLA-B27, IL-23R77, and IL-1, however, as of 2016, immunopathogenesis is unclear.
Arthritis mutilans
Scrupulosity
Arthrofibrosis
Myositis ossificans
Hypertrophic osteoarthropathy
Discoid lupus erythematosus
Tuberculous dactylitis
Myospherulosis