Psoriatic arthritis

Psoriatic arthritis is a long-term inflammatory arthritis that occurs in people affected by the autoimmune disease psoriasis. The classic feature of psoriatic arthritis is swelling of entire fingers and toes with a sausage-like appearance. This often happens in association with changes to the nails such as small depressions in the nail (pitting), thickening of the nails, and detachment of the nail from the nailbed. Skin changes consistent with psoriasis (e.g., red, scaly, and itchy plaques) frequently occur before the onset of psoriatic arthritis but psoriatic arthritis can precede the rash in 15% of affected individuals. It is classified as a type of seronegative spondyloarthropathy.Magnetic resonance image of the index finger in psoriatic arthritis (mutilans form). Shown is a T2 weighted fat suppressed sagittal image. Focal increased signal (probable erosion) is seen at the base of the middle phalanx (long thin arrow). There is synovitis at the proximal interphalangeal joint (long thick arrow) plus increased signal in the overlying soft tissues indicating edema (short thick arrow). There is also diffuse bone edema (short thin arrows) involving the head of the proximal phalanx and extending distally down the shaft.Magnetic resonance images of the fingers in psoriatic arthritis. Shown are T1 weighted axial (a) pre-contrast and (b) post-contrast images exhibiting dactylitis due to flexor tenosynovitis at the second finger with enhancement and thickening of the tendon sheath (large arrow). Synovitis is seen in the fourth proximal interphalangeal joint (small arrow).(a) T1-weighted and (b) short tau inversion recovery (STIR) magnetic resonance images of lumbar and lower thoracic spine in psoriatic arthritis. Signs of active inflammation are seen at several levels (arrows). In particular, anterior spondylitis is seen at level L1/L2 and an inflammatory Andersson lesion at the upper vertebral endplate of L3.Magnetic resonance images of sacroiliac joints. Shown are T1-weighted semi-coronal magnetic resonance images through the sacroiliac joints (a) before and (b) after intravenous contrast injection. Enhancement is seen at the right sacroiliac joint (arrow, left side of the image), indicating active sacroiliitis. Psoriatic arthritis is a long-term inflammatory arthritis that occurs in people affected by the autoimmune disease psoriasis. The classic feature of psoriatic arthritis is swelling of entire fingers and toes with a sausage-like appearance. This often happens in association with changes to the nails such as small depressions in the nail (pitting), thickening of the nails, and detachment of the nail from the nailbed. Skin changes consistent with psoriasis (e.g., red, scaly, and itchy plaques) frequently occur before the onset of psoriatic arthritis but psoriatic arthritis can precede the rash in 15% of affected individuals. It is classified as a type of seronegative spondyloarthropathy. Genetics are thought to be strongly involved in the development of psoriatic arthritis. Obesity and certain forms of psoriasis are thought to increase the risk. Psoriatic arthritis affects up to 30% of people with psoriasis and occurs in both children and adults. Approximately 40–50% of individuals with psoriatic arthritis have the HLA-B27 genotype. The condition is less common in people of Asian or African descent and affects men and women equally. Pain, swelling, or stiffness in one or more joints is commonly present in psoriatic arthritis. Psoriatic arthritis is inflammatory, and affected joints are generally red or warm to the touch. Asymmetrical oligoarthritis, defined as inflammation affecting one to four joints during the first six months of disease, is present in 70% of cases. However, in 15% of cases, the arthritis is symmetrical. The joints of the hand that is involved in psoriasis are the proximal interphalangeal (PIP), the distal interphalangeal (DIP), the metacarpophalangeal (MCP), and the wrist. Involvement of the distal interphalangeal joints (DIP) is a characteristic feature and is present in 15% of cases. In addition to affecting the joints of the hands and wrists, psoriatic arthritis may affect the fingers, nails, and skin. Sausage-like swelling in the fingers or toes, known as dactylitis, may occur. Psoriasis can also cause changes to the nails, such as pitting or separation from the nail bed, onycholysis, hyperkeratosis under the nails, and horizontal ridging. Psoriasis classically presents with scaly skin lesions, which are most commonly seen over extensor surfaces such as the scalp, natal cleft and umbilicus. In psoriatic arthritis, pain can occur in the area of the sacrum (the lower back, above the tailbone), as a result of sacroiliitis or spondylitis, which is present in 40% of cases. Pain can occur in and around the feet and ankles, especially enthesitis in the Achilles tendon (inflammation of the Achilles tendon where it inserts into the bone) or plantar fasciitis in the sole of the foot. Along with the above-noted pain and inflammation, there is extreme exhaustion that does not go away with adequate rest. The exhaustion may last for days or weeks without abatement. Psoriatic arthritis may remain mild or may progress to more destructive joint disease. Periods of active disease, or flares, will typically alternate with periods of remission. In severe forms, psoriatic arthritis may progress to arthritis mutilans which on X-ray gives a 'pencil-in-cup' appearance. Because prolonged inflammation can lead to joint damage, early diagnosis and treatment to slow or prevent joint damage is recommended. The exact causes are not yet known, but a number of genetic associations have been identified in a genome-wide association study of psoriasis and psoriatic arthritis including HLA-B27.