Psoriatic Spondylitis: A Clinical and Radiological Description of the Spine in Psoriatic Arthritis

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1 Quarterly Journal of Medicine, New Series XLVI, No. 8, pp. -5, October 977 Psoriatic Spondylitis: A Clinical and Radiological Description of the Spine in Psoriatic Arthritis J. R. LAMBERT AND V. WRIGHT From the Rheumatism Research Unit, University Department of Medicine, General Infirmary, Leeds; and The Royal Bath Hospital, Harrogate Accepted 8 April 977 SUMMARY In a review of patients with psoriatic, spondylitis was noted in per cent. Sacro-iliitis was observed in per cent and was present either when axial disease was predominant (seven patients) or in association with peripheral poly (5 patients). The groups differed in that most of those with axial disease were males who had developed psoriasis later in life. In those with disease of the axial skeleton, nail dystrophy was less common, and iritis, chronic back pain and restriction of spinal mobility were more common. They had higher values of E.S.R. In both there was a high incidence of the histocompatibility antigen B7. The axial group resembled idiopathic ankylosing spondylitis and the New York criteria were fulfilled by 8 per cent compared with 7 per cent of those who had peripheral as well. This latter group was frequently without symptoms or signs of spondylitis. Syndesmophytes are accepted as a radiological manifestation of spondylitis. They were noted in 5 per cent of patients and in per cent of these the sacroiliac joints were normal radiologically. Anterior syndesmophytes alone were found only in the cervical spine and were more common in patients without sacro-iliitis. Lateral syadesmophytes were most commonly found in the lumbar and lower dorsal vertebrae and were slightly less common in patients without sacro-iliitis. Patients with syndesmophytes and normal sacro-iliac joints had a small male preponderance. They were no more likely to have symptoms or signs of spinal disease than those with normal spine radiographs. Downloaded from by guest on May, INTRODUCTION The association of psoriasis and ankylosing spondylitis was first recorded nearly fifty years ago (Zellner, 98) and a number of case reports have followed (Bauer and Vogl, 9; Sharp and Purser, 9; Bunim, 9; Strohfeldt, 97). Boijens (99) classified 'psoriasis arthropathica' in eight types, one being associated with spondylitis though this he considered rare. This opinion was supported by several authors (Vilanova and Pinol, 95; Sherman, 95; Lassus, Mustakallio, and

2 J. R. Lambert and V. Wright Laine, 9). However, other reports contradict this (Dawson and Tyson, 98; Epstein, 99; Avila, Pugh, Slocumb, and Winkehnann, 9; Bardnagni and Carhsimo, 97) and some have demonstrated a high prevalence (Reiter and Norholm-Pedersem, 95; Sterne and Schneider, 95; Graber-Duvernay, 957; Wright, 957; Coste, Francon, Touraine, and Loyau, 958; Reed, 9; Baker, Golding, and Thompson, 9; Peterson and Silbiger, 97; Polotski, 97; Schilling and Schacherl, 97). Harvie, Lester, and Little (97) found that in patients admitted to hospital for treatment of severe psoriasis, sacro-iliitis was particularly common. The occurrence of psoriasis in patients with ankylosing spondylitis has been recorded from between two and per cent (Aalvik, 9; Clemmesen and Arns, 95; Fletcher and Rose, 955; Lefkovits and Thomas, 958;Smythe, 9). Whilst the diagnostic criteria for spondylitis and for psoriatic were not standardized in these studies their association seemed likely and Fletcher and Rose (955) proposed the term 'psoriasis spondylitica'. Wright (9) found that radiological sacro-iliitis was more common in patients with psoriatic compared with patients with rheumatoid. Dixon and Lience (9) found a higher prevalence than in a group of controls. However, Kaplan, Plotz, Nathanson, and Frank (9) found that apophyseal joint narrowing and sclerosis and anterior ligamentous calcification in the cervical spine were common in patients with psoriasis whether or not they had peripheral. The changes were indistinguishable from those of 'rheumatoid (ankylosing) spondylitis', but the lumbar spine and sacro-iliac joints were not affected. Unusual, non-marginal syndesmophytes were reported in four patients with psoriatic by Bywaters and Dixon (95). Coste and Solnica (9) reporting spondylitis in one third of patients, frequently with peripheral, noted changes in patients without symptoms and that para-vertebral ossification occurred without sacro-iliitis in some patients. Syndesmophytes and sacro-iliitis were noted in. the majority of patients with psoriatic investigated by Jajic (98). He thought the changes were distinct from those of ankylosing spondylitis. These were investigated by McEwen, Di Tata, Lingg, Porini, Good, and Rankin (97) who listed the clinical and radiological differences and similarities between the spondylitis of psoriatic or Reiter's disease and that found in ankylosing spondylitis or with chronic inflammatory bowel disease. Langeland and Roaas (97) suggested that spondylitis was associated with pustular psoriasis and that solid fusion of thoracic vertebrae, preceded by destruction of adjacent vertebral bodies, was a characteristic feature. A high prevalence of sacro-iliitis and coarse asymmetrical syndesmophytes distinguishable from idiopathic ankylosing spondylitis was reported by Killebrew, Gold, and Sholkoff (97). Sundaram and Patton (975) felt that non-marginal syndesmophytes may be the sole or major radiological abnormality of psoriatic, occurring commonly with normal sacro-iliac joints and without typical changes in the hands. On the other hand Moll (97) who drew on the literature and his personal experience felt that psoriatic spondylitis was probably a specific entity as an alternative expression of psoriatic, but that in most cases Downloaded from by guest on May,

3 Psoriatic Spondylitis there were no clinical or radiological differences from idiopathic ankylosing spondylitis. It seemed probable that psoriatic spondylitis was an entity, though the prevalence and characteristics (particularly the significance of syndesmophytes) were uncertain. We therefore reviewed patients with psoriatic with particular emphasis on clinical and radiological examination of the spine in all patients, whether or not they had symptoms. The findings were compared with those in idiopathic ankylosing spondylitis. MATERIALS AND METHODS One hundred and thirty patients (57 men and 7 women) were studied and all fulfilled the criteria of Moll and Wright (97) for psoriatic. A full history was taken and examination performed with special attention to spinal pain and mobility. Subjective assessment was made of neck movement in three planes. Circumferential chest expansion was assessed in 8 patients by the method described by Moll and Wright (97). Lumbar spinal movement was measured in three planes as detailed by Moll and Wright (97) and compared with their range of normal values. Measurements were available in 8 patients, a subjective assessment of the range of movement only having been made for the remainder. Anteroposterior radiographs of the sacro-iliac joints were available for patients, further views being taken in doubtful cases. Radiographs of the cervical spine were available for 78 patients, of the dorsal spine for 58 patients, of the lumbar spine for 8 patients and of the symphysis pubis for 57 patients. Fifty-one had radiographs of the complete spine and sacro-iliac joints. Radiographs of the peripheral joints were available for 9 patients. Seventy-eight had films of both hands and feet, of hands only and three offset only. Ankylosing spondylitis was diagnosed and graded by the New York criteria (Bennett and Wood, 98), except that assessment of joint space was not included (Macrae, Haslock, and Wright, 97). The peripheral was graded subjectively as: nil; mild (only a few joints affected with no loss of function); moderate (a few joints affected with deformity and/or loss of function, or many joints affected with only slight impairment of function); and severe (marked deformity and disability including mutilans). The values of erythrocyte sedimentation rate (ESR), haemoglobin and white blood cell count were available for all patients. Rheumatoid factor was screened in all patients by the latex fixation test and where this was positive the sheep cell agglutination titre was performed. Histocompatibility (HLA) antigen typing was performed on 8 patients and tests for anti-nuclear factor were available on 9 patients. Downloaded from by guest on May, RESULTS Radiological Features Sacro-iliitis was noted in men and women ( per cent). Table shows that changes were unilateral in five cases and bilaterally asymmetrical in five. Advanced ankylosis was found in seven patients. Sacro-iliitis was present as either a predominantly spinal disease, a form we have termed axial, or with a generalized

4 J. R. Lambert and V. Wright Fio.. Anterior syndesmophytes of dorsal spine. Downloaded from by guest on May, Fio.. Anterior syndesmophytes of cervical spine.

5 Psoriatic Spondylitis 5 TABLE. Radiological characteristics of sacro-iliitis in the varieties of spondylitis Patients with Patients with All patients sacro-iliitifl sacro-iliitis Patientfl with with and axial and peripheral syndesmophytes sacro-iliitis disease and sacro-iliitis Bilateral symmetrical sacro-iliitis 9 7 Asymmetrical sacroiliitis 5 Unilateral sacroiliitis 5 which we have termed the peripheral form. Sacro-iliitis was more likely to be unilateral in the peripheral variety. Syndesmophytes are not always distinguished easily from osteophytes or senile ankylosing hyperostosis. The problems of identification have been discussed by Riley, Ansell, and Bywaters (97), whose recommendations we followed. Syndesmophytes were found in men and women (5 per cent). Anterior syndesmophytes (Figs. and ) were found alone only in the cervical spine (eight patients), while the commonest lateral sites were the lumbar and lower thoracic regions. Marginal syndesmophytes (Fig. ) were noted in the dorsal spines of and the lumbar spines of patients. They were more common than non-marginal syndesmophytes (Fig. ) which were found in four dorsal and five lumbar spines. Non-marginal syndesmophytes were more often unilateral (four of seven cases) than were marginal syndesmophytes (five of 8 cases) though the difference was not of statistical significance. Twelve patients had. both sacro-iliitis and syndesmophytes though in 8 patients with normal sacro-iliac joints syndesmophytes were present. Table shows that there were no differences in the radiological characteristics of sacro-iliitis in those with or without syndesmophytes. The radiological features of syndesmophytes are related to sacro-iliitis in Table. Patients with normal sacro-iliac joints had a higher prevalence of only anterior syndesmophytes. Patients with peripheral were more likely to have small numbers of unilateral or asymmetrical syndesmophytes. Narrowing, erosion or sclerosis of the apophyseal joints were noted in sets of films of the cervical spine ( per cent), four of the dorsal spine (seven per cent) and five of the lumbar spine (seven per cent). Of those with cervical lesions six patients had sacro-iliitis and syndesmophytes, one patient sacro-iliitis alone, six patients syndesmophytes alone (two of these being confined to the cervical spine) and patients ( per cent) had neither. Thus patients had abnormality of the neck alone. Vertebral body squaring or erosions were seen in only patients. The cervical spine was affected infive (six per cent), the dorsal spine infive (nine per cent) and the lumbar spine in seven (ten per cent). Seven patients had sacro-iliitis, seven had syndesmophytes and two had neither. Interspinous ligamentous ossification was present in seven patients. The cervical Downloaded from by guest on May,

6 J. R. Lambert and V. Wright FIG.. Marginal symdesmophytes dorsal spine. Downloaded from by guest on May, Fio.. Non-marginal eyndesmophytes.

7 Psoriatic Spondylitis 7 TABLE. Radiological features of syndesmophytes in patients with and without sacro-iliitis All patients with psoriatic All patients with saoro-iliitis Patients with SAcro-iliitis and axial disease Patient* with sacro-iliitis and peripheral Patients with normal sacroiliac joints radiographically No. with syndesmophytes No. with anterior gyndes No. with lateral syndea No. with anterior and lateral syndes No. with unilateral syndes No. with asymmetrical syndes No. with symmetrical syndea No. with marginal syndea No. with non-marginal ayndee No. with both No. with single syndea No. with syndes No. with or more fyndes t 7 8 ot 7 S * e 7 t p < -8 compared with patients with normal saoro-iliac joints. * p < - compared with patients with sacro-iliitis and axial disease. spine was affected in four, the dorsal in three and lumbar in two. One patient did not have sacro-iliitis and one other did not have syndesmophytes. The bamboo spine appearance, typical of ankylosing spondylitis, was seen in only three patients. The symphysis pubis was abnormal in only five cases (nine per cent); one man with sacro-iliitis and syndesmophytes and three men and one woman with syndesmophytes. Intervertebral disc space narrowing was noted in the cervical spines of patients and the lumbar spines of six patients. Of these,five had sacro-iliitis and a further nine syndesmophytes. Osteophytes were seen in 5 patients. They were found in the cervical spine in cases, the dorsal spine in 8 and the lumbar spine in 7 cases. Erosion of the sternomanubrial joint was present in one female, who also had cervical syndesmophytes. Erosive changes of the extremities were present in 5 patients (8 per cent) and these affected the distal interphalangeal joints in 8 cases ( per cent). Two patients had an mutilans. Radiographs of hands and feet were available for 7 patients with syndesmophytes and normal sacro-iliac joints, and in three there was no suggestion of inflammatory at these sites. Erosive changes were present in patients (55 per cent) and affected the distal interphalangeal joints in nine (5 per cent). Nine patients with syndesmophytes and sacro-iliitis had radiographs of the hands and feet. There was no clinical suggestion of peripheral in the four for whom films were not available. Erosions were noted in four Downloaded from by guest on May,

8 to t I TABLE. Clinical features related to spondylitis No. of males No. of females Ratio males: females Mean age at review (yrs) Mean age of onset of (yrs) Mean duration of (yrs) Mean age of onset of psoriasis (yrs) Mean duration of psoriasis (yrs) % with nail involvement Mean age at onset of nail ohanges (yrs) Prevalence of iritis % All patients All patients Patients with Patients with Patients with Patients with Patients with normal spines with with sacro-iliitis sacro-iliitis syndesmophytes syndesmophytes psoriatio sacro-iliitis and axial and normal dia sacro-iliao joints : : : and peripheral 9-7: : Downloaded from by guest on May, and sacro-iliitis Clinical and Clinical radiological: and/or complete set radiological 8 : of films t 8 -: t 57 -: patients: saoro-iliac joints and some areas of spine examined by X-ray "I f 5 patients: sacro-iliac joints and whole spine examined by X-ray V Tables -7. J patients: clinical and/or radiological examination of spine J

9 Psoriatic Spondylitis 9 patients ( per cent), and this affected the distal interphalangeal joints in three ( per cent). One patient had mutilans. There is therefore no significant difference in prevalence of erosive changes related to the presence of or variety of spondylitis, though distal interphalangeal joint erosions were more frequently associated with syndesmophytes. CLINICAL FEATURES Table summarizes the clinical features and relates these to the variety of spondylitis. Females were slightly more common accounting for 5 per cent. The onset of psoriasis tended to antedate the. The prevalence of nail changes and their temporal relationship to the onset of is in keeping with that found by previous authors (Wright, 959; Baker, et ai., 9). The prevalence of iritis is the same as that in rheumatoid (Hart, 95). Patients with sacro-iliitis were older than those without spondylitis (p < -5). The sex distribution was equal and was not influenced by the presence of spondylitis. However, the group of patients in whom sacro-iliitis was present without peripheral differed from those with both sacro-iliitis and peripheral in that most were male, nail changes were less common and the psoriasis of shorter duration. These differences were significant (p < -5). The group with sacro-iliitis and axial disease differed markedly from that in which radiological sacro-iliitis was absent. Males were much more common (p < -5). Nail dystrophy was less common (p < -) and iritis was more often noted but this difference was not significant. Those with sacro-iliitis and peripheral differed from those with neither. They were older (p < -5), and the duration of psoriasis (p < -5) and (p < -) were both longer. Patients with syndesmophytes and normal sacro-iliac joints differed from those with normal radiographs, and were older at review (p < -5). Though the duration of and of psoriasis was longer, and males were dominant, these differences were not significant. There were no significant differences between the group with sacro-iliitis and that with syndesmophytes and normal sacro-iliac joints. These patients resembled the group with sacro-iliitis and peripheral. They differed from patients with sacro-iliitis without peripheral in having a greater prevalence of nail dystrophy, and an earlier onset and longer duration of psoriasis (p < -5). There were no differences between patients with both syndesmophytes and sacro-iliitis, and those with syndesmophytes and normal sacro-iliac joints. Table relates back pain and restriction of spinal movement to the varieties of spondylitis. Chest expansion was reduced in six men and six women, though two of the female patients had significant chronic obstructive airways disease. Restriction of neck movement was the most common abnormality, and nearly half the patients had persistent back pain. The prevalence of chronic back pain was higher in those with sacro-iliitis (p < -5) but this was predominantly in those with axial disease. The prevalence was no higher in those with syndesmophytes alone. Restriction of spinal mobility Downloaded from by guest on May,

10 to t I TABLE. Clinical features related to spondylitis No. of males No. of females Ratio males: females Mean age at review (yrs) Mean age of onset of (yrs) Mean duration of (yrs) Mean age of onset of psoriasis (yrs) Mean duration of psoriasis (yrs) % with nail involvement Mean age at onset of nail ohanges (yrs) Prevalence of iritis % All patients All patients Patients with Patients with Patients with Patients with Patients with normal spines with with sacro-iliitis sacro-iliitis syndesmophytes syndesmophytes psoriatio sacro-iliitis and axial and normal dia sacro-iliao joints : : : and peripheral 9-7: : Downloaded from by guest on May, and sacro-iliitis Clinical and Clinical radiological: and/or complete set radiological 8 : of films t 8 -: t 57 -: patients: saoro-iliac joints and some areas of spine examined by X-ray "I f 5 patients: sacro-iliac joints and whole spine examined by X-ray V Tables -7. J patients: clinical and/or radiological examination of spine J

11 All All Patients with Patients with Patients with Patients with Patients with normal spines patients patients sacro-iliitis sacro-iliitis syndesmophytes syndesmophytes with with and axial and and normal and sacro-iliitis Clinical and Clinical psoriatic saoro-iliitia disease peripheral sacro-iliao radiological: and/or joints complete set radiological of films to I a I TABLE. Corretation of clinical findings to varieties of radiological spondylitis Downloaded from by guest on May, Back pain-5 ft % I Chest expansion ][Vr % Neck movement i(ft 8% I Lumbar movement -j [VT 9% tf 7% ft 5% ft % ft % } % 7% $ 8% 7% T*r % ft ft 5% ft 5% T^ % ft 5% ft 8% ft 75% ft % ft 8% A 5% ft 7% TV n% ft % TV5% H % A 7% H 5% TV %

12 All All Patients with Patients with Patients with Patients with Patients with normal spines patients patients sacro-iliitis sacro-iliitis syndesmophytes syndesmophytes with with and axial and and normal and sacro-iliitis Clinical and Clinical psoriatic saoro-iliitia disease peripheral sacro-iliao radiological: and/or joints complete set radiological of films to I a I TABLE. Corretation of clinical findings to varieties of radiological spondylitis Downloaded from by guest on May, Back pain-5 ft % I Chest expansion ][Vr % Neck movement i(ft 8% I Lumbar movement -j [VT 9% tf 7% ft 5% ft % ft % } % 7% $ 8% 7% T*r % ft ft 5% ft 5% T^ % ft 5% ft 8% ft 75% ft % ft 8% A 5% ft 7% TV n% ft % TV5% H % A 7% H 5% TV %

13 TABLE 5. Blood tests related to radiological type of spondylitis All All Patients with Patients with Patients with Patients with Patients with normal spines patients patients sacro-iliitis sacro-iliitis syndesmophytes syndesmophytes - with with and axial and and normal and sacro-iliitis Clinical and Clinical psoriatic sacro-iliitis disease peripheral sacro-iliac joints Downloaded from by guest on May, radiological: complete set of films and/or radiological Rh. Factor HLAB7 ANF E.S.R. < H -rh % r -5% % % 8% % H 7% 5 % 5% % 8% 9% 7% % 9% 9% 9% % 9 8% 9% 5% % I 78% Hb -5% 9% 9% 7% % % % 7% W.C.C. > 5 % 5% 7% % 5% % % % % % 9% 5% 7% % 8 5 8% % 8% % 9% 9% 8 8 9% % % 7% % %

14 J. R. Lambert and V. Wright was associated with the axial form of disease with sacro-iliitis, though restricted neck movement was also found in those with both peripheral disease and sacroiliitis. Patients with syndesmophytes showed no greater tendency to restricted movement compared with those with normal films. The New York criteria (Bennett and Wood, 98) for ankylosing spondylitis was fulfilled by patients, six with axial sacro-iliitis and four with peripheral sacroiliitis. Blood tests These are tabulated and related to the form of spondylitis in Table 5. Tests for rheumatoid factor were negative in all cases though two females had had low titres (: and :8) at the onset of. HLA-B7 was present in patients ( per cent), significantly more than in controls (7 per cent, p < -5). The prevalence of positive tests for anti-nuclear factor is that expected in the general population. Only two patients had significant anaemia (haemoglobin less than llg d I" in males or G d I" in females). Both of these had sacro-iliitis and syndesmophytes and predominantly axial disease. The prevalence of HLA-B7 was raised in patients with sacro-iliitis and either peripheral or axial disease. Table relates the presence and severity of peripheral to spinal disease. Patients with sacro-iliitis and axial disease had by definition a milder peripheral disease, though there were no other differences. The severity of psoriasis is related to spinal disease in Table 7. There are no significant differences between the various groups. The prevalence of iritis was high only in patients with sacro-iliitis and predominantly axial disease and less so in those with both sacro-iliitis and syndesmophytes (Table ). No patient had an abnormal heart. Downloaded from by guest on May, DISCUSSION The high prevalence of sacro-iliitis at about per cent is similar to that reported by TTill (9) and Baker, Golding, and Thompson (9), though higher than reported by Dawson and Tyson (98), Avila et al. (9), Bardnagni et al. (97). The significance of syndesmophytes in psoriatic is uncertain; they may represent inflammatory or degenerative spinal disease. Though we ignored doubtful cases the presence of syndesmophytes, unlike that of sacro-iliitis, was not related to back pain or restricted spinal mobility. Syndesmophytes are not included in the diagnostic criteria of ankylosing spondylitis (Kellgren, 9; Bennett and Wood, 98), but are generally accepted as a manifestation of spondylitis (Collins, 99; Romanus and Ydens, 955; McEwen et al, 97). The pathogenesis of syndesmophytes in psoriatic spondylitis is unknown. It has been suggested that the calcification may result from an inflammatory process in paravertebral connective tissues or be a form of periosteal reaction secondary to traction on bone (Bywaters and Dixon, 955), or there may be an enthesopathy as described in ankylosing spondylitis (Ball, 97) but with a different distribution.

15 (%) (9%) (9%) 55 (%) (%) (%) to w TABLE. Severity of peripheral related to radiological changes Peripheral Arthritia Nil Mild Moderate Severe All patients with psoriatio (5%) 57 (%) 9 (8%) 8 (%) All patients with sacro-iliitis (8%) (5%) 5 (%) (%) Patients w: sacro-iliitis and axial disease (%) (57%) Patients with Patients with Patients with Patients with normal spines sacro-iliitis syndesmophytes syndesmophytes and and normal and sacro-iliitis Clinical and Clinical peripheral sacro-iliao joints radiological: and/or complete radiological set of films (7%) (%) (%) (%) 8 (%) 7 (9%) (7%) Downloaded from by guest on May, (5%) 5 (%) (7%) (7%) (5%) 7 (%) (8%) (%) (%) 9 (%) 7 (%) (%) a s- TABLE 7. Severity of psoriasis related to radiological changes All patients with psoriatio All patients with sacro-iliitis Patients with sacro-iliitis and axial disease Patients with sacro-iliitis and peripheral Patients with Patients with Patients with normal spines syndesmophytes syndesmophytes ^ and normal and sacro-iliitis Clinical and Clinical sacro-iliao joints radiological: complete set of films and/or radiologioal Mild Moderate Severe 8 (%) 9 (%) 9 (7%) 8 (8%) (9%) (9%) (8%) (%) (8%) (7%) (%) 9 (5%) 7 (9%) (%) 9 (75%) (7%) (8%)

16 J. B. Lambert and V. Wright That syndesmophytes are not degenerative in origin is suggested by their occurrence in a group younger than the group with normal spines. Their association with HLA-B7 is further evidence of the aetiological similarity to ankylosing spondylitis. It seems, therefore, that in their presence a presumption of spondylitis is reasonable even in the absence of sacro-iliitis. Those patients with sacro-iliitis fall readily into two groups; those in whom spinal was the major disability and those in whom there was a significant peripheral. The two groups differ clinically and radiologically. Those with mainly spinal resembled idiopathic ankylosing spondylitis, with a male dominance, high prevalence of iritis, a lower prevalence of nail dystrophy, and shorter duration of psoriasis. It is of interest that HLA-B7 was found in a similar proportion of both groups, while clinical symptoms and signs of spondylitis were more common in the axial group, in which disease activity as indicated by the E.S.R. was low. It is likely that the axial group represent the chance association of psoriasis and ankylosing spondylitis, the prevalence being about 7 per cent. Psoriatic spondylitis is characterized radiologically by sacro-iliitis and by syndesmophytes. This differs from ankylosing spondylitis clinically and radiologically. There was no sex difference and the mean age of onset of was higher. Spondylitis usually caused no symptoms and no signs of restricted spinal mobility. Peripheral was more extensive and a more important aspect of the disease than in ankylosing spondylitis. Extra-articular manifestations were not encountered. Sacro-iliitis was more frequently unilateral or asymmetrical and syndesmophytes which occurred in small numbers, were unilateral or asymmetrical and were more often non-marginal. HLA-B7 was associated with sacro-iliitis and was present more often than normal in those with only syndesmophytes. REFERENCES AALVTK, T., 9. Nord. med. 5, 7. AVTLA, R., PTJGH, D. G., SLOCUMB, C. H. and WLNXELMANN, R. K., 9. Radiology, 75, 9. BAKER, H., GOLDING, D. N., and THOMPSON, M., 9. Ann. intern. Med. 58, Brit. J. Derm. 7, 59. BALL, J., 97. Ann. rheum. Dis.,. BABDNAGNI, O., and CXSLISIMO, O. A., 97. Policlinico, Sez. prat. 7,. BAUER, J., and VOGL, A. 9. Klin. Wschr., 7. BENNETT, P. H., and WOOD, P. N. H. (editors) 98. "Population studies of the rheumatic diseases", Proc. rd Int. Symp., New York, 9. Int. Congr. p. 5. Ser. No. 8. Amsterdam, Excerpta Medica Foundation. BOIJENS, F. VAN DEB, 99. "La rheumatism psoriatique". Paris, de Francois. BOTJIM, J. J., 9. Ann. intern. Med. 57, 8. BYWAXEBS, E. G. L., and DIXON, A. St. J., 95. Ann. rheum. Dis.,. CLEMMESEN, S., and ABNSO, E., 95. "Rheumatic Diseases": based on the Proceedings of the 7th Int. Congr. on Rh. Dis. p. 5, Philadelphia, Saunders. COLLINS, D. H., 99. "The pathology of articular and spinal diseases". st Edition, London, Arnold. COSTE, F., FBANCON, J., TOUBAINE, R., and LOYATJ, G., 958. Rev. Rhum. 5, 75. and SOLNICA, J., 9. Rev.franc, fitud. din. biol., 578. DAWSON, M. H., and TYSON, T. L., 98. Trans. Ass. Amer. Phycns. 5,. DIXON, A. ST. J., and LIENOE, E., 9. Ann. rheum. Dis., 7. EPSTEIN, E., 99. Arch. Derm. Syph. (Chic.), 57. FLETCHEB, E., and Rose, F. C, 955. Lancet, i, 95. Downloaded from by guest on May,

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