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Information for Doctors

Psoriatic arthritis
Information
Etiology and pathogenesis
Pathology
Clinical picture
Laboratory findings
X-ray findings
D/D of arthritis mutilans
Disorders associated with HLA antigens
Prognosis
D/D of distal phalangeal (TUFT) resorption
Differential diagnosis
Treatment protocol
Outcome of joint replacement surgery in psoaritic spondylo arthropathies
Role of corticosteroids
Role of surgery
Role of antipsoaritic therapy
It is an inflammatory erosive arthritis that affect 5 to 10% of people with psoriasis.

Etiology and pathogenesis:

Exact etiology is not known, mechanisms postulated being,

  1. Infection
  2. Trauma
  3. Increased cellular immunity (e.g. to streptococci)
  4. Increased supressor cell activation
  5. Abnormal fibroblast and polymorphonuclear leukocyte function

Increased frequency of histocompatibility antigen HLA B27 has been found with psoaritic arthritis whereas it is absent in pure cuteneous psoriasis.

Pathology:

It is similar to that seen in rheumatoid arthritis: synoviocytic hyperplasia, early polymorph infiltration, later mononuclear cell infilteration, cartilage erosion. In contrast to RA pannus formation, dense accumulation of round cells and osteoporosis are never observed. Fibrosis of the joint capsule and marrow is prominent in many patient. The inflammatory tissue which erodes the cortex and articular cartilage at the periphery of articular end of the bone, tends to extend along the surface of the shaft eroding it from without causing the characteristic scalloped appearance.

Clinical Picture:

The arthritic manifestion usually develop after about 10-12 year of development of skin lesion, especially common with extensive skin involvement. An apparent psoriatic arthritis without skin lesion usually reveals hidden skin lesion on detailed examination.

Almost invariably onychodystrophy (onycholysis, ridging a pitting of nails) is associated.

The onset may be gradual or acute (resembling gout). The syndrome has remission and exacerbations. The proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints are commonly involved (With) characteristic sausage shaped digits (dactylitis)] while knees, hip, ankle, temporomandibular joints and wrists are less frequently involved.

Enthesopathy (inflammation of tendon and ligaments attachments to bone) is characteristic for e.g. of tendoachillis, planter fascia causing

Five clinical group can be divided:

  1. Classic psoriatic arthropathy (5%): It predominantly affect the DIP joints.
  2. Arthritis mutilans (5%): Severe osteolysis affecting the DIP, PIP and MCP joint of the hand producing marked digital telescoping associated with acroosteolysis of the shafts of the distal phalanges produce an extremely unstable deformity of many digits known as arthritis mutilans.
  3. Symmetrical polyarthritis (15%): Similar to rheumatoid arthritis but lacks rheumatoid nodules and serology is negative.
  4. Asymmetrical oligoarticular or monoarticular arthritis (10%): Affects scattered DIP, PIP, MCP joints. Associated effusion of a flexor sheath may lead to sausage shaped digits.
  5. Ankylosing spondylitis or sacroilitis (5%): Here the back pain is minimal compared to AS.

Laboratory findings:

Salient features are :

  1. High incidence of HLA B27
  2. Normal ESR in pure cutaneous psoriasis and elevated when arthritis develops
  3. Anemia is common and parallels the severity of arthritis
  4. Hyperuricemia is also very common, absence of sodium urate crystals in joints differentiate it from gout
  5. ANA may be occasionally found in patient with extensive psoriasis

X-rays finding:

Salient feature are

  1. Erosion and narrowing of small fingers and toe joints with sometimes bony ankylosis and subluxations
  2. Dissolution of terminal phalangeal tufts (acroosteolysis)
  3. Penicilling (tapering) of phalanges, metacarpals and metatarsals with cupping of proximal ends of phalanges, metacarpals and metatarsals. When pencil shaped end of bone articulate with cup shaped erosion of distal bone the typical deformity is called 'pencil -in -cup' deformity.
  4. There is more predilection for DIP and PIP joints with releative sparing of MCP joints.
  5. Changes in axial skeleton include

a.       Asymmetric or unilateral sacroilitis

b.      Asymptomatic paravertebral ossification

c.       Large asymmetric non marginal syndesmophyte

  1. In early stages only juxtarticular soft tissue swelling and minimal joint erosions may be seen. Commonest radiography finding in psoaritic arthritis is symmetrical destruction of small isolated joints and an oligoarticular involvement.

D/D of arthritis mutilans:

  1. Psoriatic arthropathy
  2. Rheumatoid arthritis
  3. Juveline chronic arthritis
  4. Neuropathic arthropathy
  5. Leprosy
  6. Diabetes mellitus
  7. Reiter's syndrome

Disorders associated with HLA antigens:

  1. Rheumatic diseases: Ankylosing spondylitis and related disorders

  2. Gastrointestinal diseases: Gluten-sensitive enteropathy, pernicious anaemia, chronic active hepatitis, hemochromatosis

  3. Immunopathic diseases: SLE, Sjogren's disease

  4. Neurologic disease: Multiple sclerosis, myasthenia gravis

  5. Skin diseases: Psoriasis, discoid lupus enythematosus, behcet's disease.

  6. Endocrine disorders: IDDM, Grave's disease, addison's disease.

  7. Malignant diseases: Hodgekin's, acute lymphoblastic leukemia

  8. Drug reactions: Hydralazine, lupus

Prognosis:

Psoriatic arthritis is highly vulnerable to trauma the resulting inflammation tending to persist for long period.

Prognosis of arthritis is good, with only one fourth of the patient developing progressive destruction. One third develop inflammatory ocular complication (conjuctivitis, iritis, episcleritis).

D/D of distal phalangeal (TUFT) resorption:

  1. Psoriatic arthropathy
  2. Hyperparathyroidism
  3. Epidennolysis bullosa
  4. Neuropathic: Leprosy, syringomyelia, diabetes, myelomeningocele
  5. Trauma
  6. Raynaud's disease
  7. Thermal injury
  8. Sclerodenna

Differential diagnosis:

  1. Arthritis with nonpsoaritic skin lesion: Psoariasis should be differentiated from seborrheic dermititis and eczema. Fungal infection of nails can be distinguished by absence of pitting and onycholysis
  2. Reiter's syndrome: It occurs in younger individuals especially males, is less frequently progressive or distructive and is associated with arthritis, conjuctivitis, keratodema blenorrhagica.
  3. RA: It can be differentiated by tendency to iritis, dactylitis enthsopathy, nail lesion, high incidence of absence of RA factor and x-rays feature. Rheumatoid nodules are never found. Hand deformities such as swan-neck deformity, boutonniere deformity, ulnar deviation of finger are very rare. Presence of HLAB27 antigen rules out rheumatoid arthritis.
Treatment Protocol :
Refer to Chart : Click here

Outcome of joint replacement surgery in psoaritic spondylo arthropathies:

Patient with psoriatic arthritis undergoing joint surgery have been thought to be at risk of wound infection from the heavy bacterial contamination of psoriatic plagues. The problem of infection may be controlled by careful antiseptic skin preperation and perioperative antibiotics therapy against common psoriasis contaminants (Staphylocacci and streptococci).

Role of corticosteroids:

A good clinical response is usually elicited with prednisolon 40mg daily which can be gradually tapered to maintenance dose for around 6-10 wks. There after drug can be gradually withdrawn. In a refractory case of synovitis, intraarticular steroid may be used.

Role of surgery:

The surgical treatment is similar to that of rheumatoid arthritis. Increased incidence of infection following joint replacement has been reported in literature.

Role of antipsoaritic therapy:

Photochemotherapy (ultraviolet light plus methoxsalen) has a beneficial effect on arthritis also.

IMP. Tips:

  1. Sapho: It is a subset of psoaritic arthritis consisting of synovitis acne, pustulosis, hyperostosis and osteomyelitis.
  2. If following trauma, pain in a joint persist for a long time without any clinical or radiographic evidence of bone or joint injury, one must look for possible lesion of cutaneous psoriasis