A classic case of psoriatic arthropathy

Clinical History

A 53-year-old male patient came to our hospital with complains of painful progressive fixed joint deformities in the hands for the past three years. On examination the patient had onycholysis, subungual keratosis, reddish itchy patches with scaling on the scalp.

Imaging Findings

X-rays revealed changes of bilateral asymmetrical involvement of the distal interphalangeal joints of both hands with marginal erosions and fluffy periostitis. ‘Pencil in cup’ deformity was seen in few PIP joints (Fig. 2). Bony ankylosis was seen involving carpal bones and few digits (Fig. 3). Classic ray sign with involvement of all joints of a finger was seen (Fig. 3). Flexion deformity was seen involving fourth and fifth digits of both hands and the wrist joint (Fig. 3).
Marginal erosions with preserved bone density and enthesophytes were seen in the foot (Fig. 4).
Bilateral asymmetrical sacroiliitis with more involvement of the right side was seen (Fig. 5).
Non-marginal osteophytes were seen in the cervical and lumbar spine (Fig. 6 and 7).

Discussion

Psoriasis is a skin disorder characterized by scaling rashes, nail changes and seronegative arthropathy. The patient present with itchy rashes, painful joint swelling and nail changes [1]. The exact pathophysiology of psoriasis and psoriatic arthropathy is unknown, however, various genetic and environmental factors have been associated. Various Human Leukocyte Antigens (HLA) have been associated with the disease but most common is HLA- B27 [2]. HLA Cw6 is associated with earlier development of skin changes and time dependent changes of arthritis [3].
Psoriasis is a debilitating multisystem disorder which can occur at any age but affects older adults and elderly patients with no gender predilection. The global burden of disease ranges from 0.09 to 11.4% [4].
Psoriatic arthropathy is an inflammatory seronegative arthropathy. It involves distal peripheral joints in hand and feet most commonly. It commonly affects sacroiliac joints and spine. Other less commonly involved joints include ankle, knee, elbow and shoulder joints. [5]
CASPER-Classification criteria for psoriatic arthritis are used for diagnosing psoriatic arthropathy in any patient presenting with inflammatory arthritis, which include psoriatic skin changes or family history, psoriatic nail dystrophy, negative rheumatoid factor, dactylitis and juxtaarticular new bone formation other than osteophytes.
There are five main subtypes of psoriatic arthropathy according to Moll and Wright: (A) Symmetrical peripheral polyarthropathy resembling RA, (B) Asymmetrical oligo or mono arthritis, (C) Axial spondyloarthropathy, (D) Predominant DIP joint involvement, (E) Arthritis mutilans.
The radiological hallmark of psoriatic arthropathy is bilateral asymmetrical disease with involvement of distal interphalangeal joints, bone proliferation, enthesitis and preserved bone density. Involvement of distal interphalangeal joint more than metacarpophalangeal joint is diagnostic. Various classic signs described are - Classic erosions with new bone formation in form of fluffy periostitis termed ‘mouse ear’ sign. Ray sign is involvement all joints of a digit and is diagnostic of psoriasis. Sausage digits occur due to commonly seen dactylitis. Bilateral asymmetrical sacroiliitis is seen [6]. Spine involvement seen as non-marginal syndesmophytes, squaring of vertebrae and bamboo spine but are less severe and less common than ankylosing spondylitis. Later in the course of the disease ‘pencil in cup’ deformity, lanois deformity and eventually bony ankylosis occurs.
Early identification of joint involvement with implementation of proper drug therapy regimens and physiotherapy help cease the progression of disease and reduce patient debilitation and morbidity.
Clinical examination and history are of paramount importance along with radiological examination, especially when the disease presents as RA-like picture.

Differential Diagnosis List

Final Diagnosis

Psoriatic arthropathy

URL:	https://www.eurorad.org/case/14662
DOI:	10.1594/EURORAD/CASE.14662
ISSN:	1563-4086