|Year : 1997 | Volume
| Issue : 6 | Page : 357-360
Psoriatic arthropathy : A clinical and biochemical study
EG Anuja, PA Sarojini
E G Anuja
Source of Support: None, Conflict of Interest: None
39 psoriatic patients with arthropathy and a negative rheumatoid factor were analysed to find the types of arthropathy and psoriasis and also any associated bichemical changes which could indicate the risk of developing arthropathy. All 5 types of arthropathy were noted, though the asymmetrical mono or oligo articular type was the most common and psoriasis vulgaris with nail involvement was more commonly associated with arthropathy. A significant association between serum hypocalcemia and psoriatic arthropathy was observed.
Keywords: Psoriatic arthropathy, Hypocalcemia
|How to cite this article:|
Anuja E G, Sarojini P A. Psoriatic arthropathy : A clinical and biochemical study. Indian J Dermatol Venereol Leprol 1997;63:357-60
|How to cite this URL:|
Anuja E G, Sarojini P A. Psoriatic arthropathy : A clinical and biochemical study. Indian J Dermatol Venereol Leprol [serial online] 1997 [cited 2020 Jun 6];63:357-60. Available from: http://www.ijdvl.com/text.asp?1997/63/6/357/4617
Psoriatic arthropathy (PA) is defined as the association of psoriasis of skin and / or nails with peripheral and / or spinal arthropathy and usually with a negative serological test for rheumatoid factor  Though wide variation in prevalence rates from 0.5-40.2% are reported  studies from India have shown a prevalence of 2.2-6% ,, PA are of 5 main types - (1) mono or asymmetrical oligo arthropathy involving mainly single joint or a few small joints of hands and feet (50-70%) (2) the classical type which predominantly involves distal interphalangeal (DIP) joint (5%) (3) arthropathy resembling rheumatoid arthritis (4) psoriatic arthritis mutilans (5%) and (5) the type where ankylosing spondylitis (AS) and / or sacroiliitis (SI) predominates (30%).
| Materials and Methods|| |
The study included all psoriatic patients having skin and / or nail lesions with joint complaints attending the Dermatology OPD during a one year period as well as all seronegative patients with arthritis attending rheumatology clinic who were detected to have some evidence of psoriasis. The criteria by Moll and Wright  were employed to include the cases.
A detailed history and examination of skin, nail, mucosa and joints were done. The number of joints involved as well as symptoms and signs like pain, tenderness, swelling, redness, warmth and limitation of motion were noted and categorised into the 5 groups.
Investigations on urine and blood including serum calcium, phosphorus, uric acid, total proteins and albumin, latex fixation test for rheumatoid factor and blood VDRL were done. Biopsy of skin and other relevant investigations were done. wherever necessary and radiological studies of all affected joints were also done. These were compared with a matched control group of 28 psoriatic patients without arthropathy.
| Results|| |
Out of the 13507 new out patients, 366 (2.71%) had psoriasis, among whom, 39 (10.66%) had arthropathy, constituting 0.29% of the total new patients and 16.8% of psoriasis patients. The male to female ratio was 1 . 44 : 1. The age at onset of PA ranged between 13 and 67 years, majority were between 29-55 years.
Arthritis followed the onset of skin or nail lesions in 74.36% patients, while it preceded in 12.8% and occurred simultaneously in the rest (12.84%). The majority of patients (53.85%) had arthritis of less than one year, while skin lesions varied from 4 months to 16 years and nail lesions between 2 months to 15 years.
With the exception of the wrist and temporomandibular joints, all joints of the body were involved. Monoarticular or asymmetrical oligoarticular type of arthropathy was commonest (84.62%) with the knee being the most affected (66.67). Distal interphalangeal (DIP) joint involvement was seen in 53.85% and it was the only joint affected in 15.38%. Arthritis mutilans was seen in 7.69%, and rheumatoid type in 5.13%. The majority of arthropathic patients had psoriasis vulgaris (74.49%), while exfoliative and palmoplantar psoriasis was seen in 7.69% only. One person with exfoliative psoriasis and two with psoriasis vulgaris developed arthritis mutilans [Figure - 1]. Two persons (5.13%) showed only nail changes of psoriasis and no case of pustular psoriasis was associated with arthropathy. Nails were the commonest site of involvement (87.17%), that of fingers more than toes. All patients with DIP involvement showed changes in the corresponding nails. The changes were nail dystrophy (70.59%) followed by onycholysis, pitting, yellowish discolouration, subungual hyperkeratosis and ridging. The limbs were the most affected site of skin lesions (74.36%), next being scalp, trunk, soles and palms. Oral mucosal involvement in the form of fissuring of tongue was noted in 15 patients (38.46%).
Investigations on urine and blood were normal except for raised ESR in 69.23% patients. Blood VDRL was nonreactive and the rheumatoid factor was negative in all. The serum calcium levels (corrected in accordance with serum proteins) was markedly reduced (< 8.4mg%) in 16 patients and moderately (8.5-9mg%) in another 9 patients. Thus, 64.1% of the arthropathic patients had hypocalcemia as compared to only 17.86% of the control patients and this difference was found to be statistically significant (p < 0.001 by Chi square test). The mean serum calcium levels of 8.74 mg% in arthropathic patients was also significantly lower than that of 9.53mg% in control patients (p < 0.001 by test). The serum levels of phosphorus, protein and uric acid did not show any significant abnormality.
Radiological changes were noted in only 10 patients (25.64%). Eight persons with clinical involvement of DIP joints showed soft tissue swelling, erosions of juxta articular areas with narrowing of joint space and erosion of base of distal and proximal phalanges. Widening of the base of the distal phalanx, fish-tail deformity, acro-osteolysis, whittling and pencil-in-cup deformity, subluxation, fixed deformities and bony ankylosis of IP joints were also noted [Figure - 2].
Wrist joint, though clinically uninvolved, showed mild osteoporosis of distal end of radius and erosion of ulnar styloid in 2 patients. Deformities, overriding of toes with involvement of IP joint of big toe, calcaneal spurs, periosteal reaction at site of attachment of Achilles tendon and over lateral malleoli were also noted. There was no involvement of axial skeleton or sacroiliac joints.
| Discussion|| |
The occurrence of arthropathy among psoriatic patients noted in this study is slightly higher than the previous reports from India. If skin lesions are hidden, minimal or in temporary remission, diagnosis of PA can be missed and this may explain the wide variations in prevalence rates in different studies. The diagnosis is also likely to be missed in a minority of patients in whom, skin or nail lesions develop after the onset of PA or only nail changes are present as in two patients in this study. This calls for a thorough clinical and laboratory examination of all suspected cases. The classical type of PA showed a higher than usual incidence and could be due to the triggering effect of trauma. That the deforming and mutilating type of arthropathy was low, indicates that PA, though chronic, is generally less incapacitating and of better prognosis than other arthropathies. Psoriasis vulgaris was found to be the commonest type associated with PA, unlike the expected pustular and exfoliative psoriasis.  Nail lesions are more associated with PA and all the corresponding nails in patients with DIP involvement were affected, possibly due to increased trauma at these areas. Thus nail involvement may indicate a risk for developing PA.
There is no difinite diagnostic investigation for PA. Rheumatoid factor should be negative. Radiological evidence may be lacking in most patients and should not be taken as exclusion criteria.
A significant association between lowered serum calcium and PA is not well documented, though its association with pustular psoriasis is well known.  The exact cause of serum hypocalcemia is not known and whether hypocalcemia is the result of, or contributory to the development of psoriatic arthropathy is not definite. If it is contributory, then calcium supplements should alleviate arthropathy, but since the study did not include the treatment and its follow up, the exact role of hypocalcemia remains speculative. Hence it would be worthwhile to do further controlled multicentric studies on this aspect.
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[Figure - 1], [Figure - 2]