Types of Psoriatic Arthritis

A] Asymmetrical Oligoarticular Arthritis: this is the commonest type and seen in 60 % of patients up to five small joints are involved.
The affection of joints is asymmetrical and involves a few scattered distal interphalangeal (DIP), proximal interphalangeal (PIP) and metacarpophalangeal (MCP) joints, knees, ankles, and feet.

They are often associated with dactylitis, which presents with diffuse swelling of one or more fingers and toes in a sausage digit configuration.
This diffuse swelling is due to the intense and diffuse inflammatory changes that occur in the joints and soft tissues and is not present in RA.

B] Symmetrical Polyarthritis: The hands, wrists, ankles, and feet may be involved.
It is differentiated from rheumatoid arthritis (RA) by the presence of distal interphalangeal (DIP) joint involvement, the relative asymmetry, the absence of subcutaneous nodules, and a negative test result for rheumatoid factor. This condition generally is milder than RA, with less deformity.

C] Distal interphalangeal-arthropathy: DIP joint involvement is considered classic and unique to psoriatic arthritis; it occurs in around 5-10% of patients, primarily men and is characterized by inflammation and stiffness in the joints nearest to the ends of the fingers and toes. Digits affected have characteristic psoriatic nail changes. These patients may or may not have skin lesions of Psoriasis.

D] Arthritis Mutilans: This is a very destructive form of arthritis, which can cause rapid damage to the joints.
It affects 5 % of all cases of Psoriatic Arthritis.

Resorption of bone (osteolysis) with the dissolution of the joint, observed as the "pencil-in-cup" radiographic finding is most commonly seen in the fingers and toes.

E] Spondylitis with or without sacroiliitis: Clinical evidence of spondylitis, sacroiliitis, or both can occur in conjunction with other subgroups of psoriatic arthritis.
Spondylitis may occur without radiological evidence of sacroiliitis, which frequently tends to be asymmetric, or it may appear radiological without the classic symptoms of morning stiffness in the lower back. Thus, the correlation between symptoms and radiological signs of sacroiliitis can be poor.
Vertebral involvement differs from that observed in Ankylosing spondylitis. Vertebrae are affected asymmetrically, and the atlantoaxial joint may be involved with the erosion of the odontoid and subluxation.

F] Juvenile Psoriatic Arthritis: Juvenile psoriatic arthritis affects 10-20 % of children suffering from arthritis and is monoarticular at the onset.
The mean age of onset is 9-10 years. The disease is usually mild, although occasionally it may be severe and destructive.

In patients presenting with an undefined seronegative polyarthritis, looking for psoriasis in hidden sites such as the scalp (where psoriasis is frequently mistaken for dandruff), perineum, intergluteal cleft (the groove or crack between the buttocks) and umbilicus is extremely important.

G] Nail involvement includes the following:

01 Onycholysis: Onycholysis is the gradual and painless separation of the nail plate from the nail bed. The nail gets lifted from its bed at its end and presents an irregular border between the pink portion of the nail, the white outside edge of itself and a greater portion of the nail is opaque. In some rare cases of Onycholysis, the spontaneous nail plate separation can be confined to the nails lateral borders although it usually starts at the distal free margin and progressing proximally.

02 Transverse ridging, and

03 Uniform nails pitting; are 3 features of nail involvement that should be noted.

When skin and joint disease begin simultaneously, nail involvement is frequently present at the onset.

Nails are involved in 80% of patients with psoriatic arthritis but in only 20% of patients with uncomplicated psoriasis.

Severe deforming arthritis of the hands and feet is frequently associated with extensive nail involvement.

H] Ocular involvement may occur in 20% of patients with psoriatic arthritis, including conjunctivitis in 20% and acute anterior uveitis in 7%.
Uveitis should be managed by an ophthalmologist.