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Bone scintigraphs obtained with both Technetium-99m polyphosphate and Technetium-99m pyrophosphate have been abnormal at the sacroiliac joints of 44 patients with definite ankylosing spondylitis (AS). Because of the normal registration of the sacroiliac joints on bone scintigraphy, it has been necessary to develop a profile-scan technique to quantify the abnormality that proves to be significantly different from the normal finding. In 17 patients with a strong clinical suspicion of AS but normal radiographs, the sacroiliac joints have frequently been abnormal. This finding is meaningful because there is a common occurence in this group of the histocompatibility antigen HL A-B27, known to be a marker of AS. We also note the frequency of abnormal sacroiliac scinitigrams in 26 patients with rheumatoid arthritis and in a group of other diseases-Crohn's disease, uveitis, psoriasis, ulcerative colitis, and Reiter's disease-all of which share some of the manifestations of AS.

An attempt has been made to improve diagnostic precision in a group of diseases associated with inflammation of the sacroiliac joints, by using a 99mTechnetium stannous pyrophosphate bone scan. Inflammation of these joints is associated with osteoblastic activity and is reflected by an increase in the uptake of radionuclide, which can be precisely quantitated. The uptake was markedly above the range of normal in patients with active ankylosing spondylitis (AS), and also in a number of patients with possible AS, psoriasis, and Reiter's syndrome. However, patients with Grade 4 radiological changes of the sacroiliac joints frequently had normal scans. This technique may be useful in the early diagnosis of sacroiliitis, and the nosological implications of the changes in patients with Reiter's syndrome and psoriasis are of interest.

HLA-B27 is a transplantation antigen found in a high proportion of patients with ankylosing spondylitis. Recently, an association has been shown to exist between HLA-B27 and acute uveitis, even in the absence of ankylosing spondylitis. We have examined the HLA antigen profile of 45 patients with acute nongranulomatous anterior uveitis and have confirmed this relation. In addition, using 90mtechnetium stannous pyrophosphate we have been able to demonstrate abnormal bone scan in 19 of 30 patients studied. Such abnormalities are limited to the sacroiliac joints but are otherwise the same as those seen in overt ankylosing spondylitis. Seven of the 19 patients did not have HLA-B27. These factors suggest that acute anterior uveitis may often represent a manifestation of a spondylitic diathesis even in the complete absence of any suggestive symptomatic or radiologic change and, in some cases, even though the antigenic marker HLA-B27 may be absent.

An attempt has been made to improve diagnostic precision in a group of diseases associated with inflammation of the sacroiliac joints by using a 99mtechnetium stannous pyrophosphate bone scan. Inflammation of these joints is associated with osteoblastic activity and is reflected by an increase in the uptake of radionuclide, which can be precisely quantitated. The uptake was markedly above the range of normal in patients with active ankylosing spondylitis (AS), and also in a number of patients with possible AS, psoriasis, and Reiter's syndrome. However, patients with Grade 4 radiological changes of the sacroiliac joints frequently had normal scans. This technique may be useful in the early diagnosis of sacroiliitis, and the nosological implications of the changes in patients with Reiter's syndrome and psoriasis are of interest.

Twenty-four patients had abnormal sacroiliac joints detected by quantitative sacroiliac scintigraphy but no radiological evidence of sacroiliitis on original investigation. We studied them again after intervals of 12 to 36 months. Four patients developed radiological change. Two young, HLA B27-positive men had undoubted ankylosing spondylitis, and a young woman had possible ankylosing spondylitis. A middle-aged man had changes that could be attributed to post-traumatic osteoarthrosis. Of the remaining 20 cases 15 had symptoms and signs suggestive of inflammatory disease of the axial skeleton (and peripheral arthropathy in 5 cases). The sexes were affected equally (8 females, 7 males), and only 2 of the 15 were B27-positive. The response to anti-inflammatory medication was generally good to excellent, and scintiscans tended to improve. Of the remaining 5 patients, 3 had mechanical or traumatic problems, and in 2 there was no explanation for the abnormal sacroiliac scintiscan. We conclude that quantitative sacroiliac scintigraphy may detect ankylosing spondylitis prior to the develpment of radiological change and that it can identify an organic basis for backache in patients with a spondylitis-like syndrome. The clinical circumstances must be taken into account, as scintigraphic abnormalities are not diagnostic of any specific disease entity.

Sacroiliitis can be demonstrated radiologically in over one-third of patients with chronic Reiter's syndrome. We have used a bone scan technique with digital analysis which will quantitatively assess the sacroiliac joints, and have found abnormalities in 24 of 33 patients with active Reiter's syndrome. It seems likely therefore that sacroiliitis is a common feature in patients with early Reiter's syndrome and while in most patients it resolves with resolution of disease activity, in some it may persist with the development of overt radiological changes.