Ankylosing spondylitis (AS) is a rheumatic disease mainly affecting the axial skeleton that is characterized by sacroiliitis in earlier disease stages (a major diagnostic criteria). In the field of paleopathology, inappropriate identification of AS usually results in missed diagnosis or misdiagnosis, and thus we have established new criteria for diagnosing AS in ancient human remains employing advances in clinical medicine and medical imagery. The criteria were as follows: 1) sacroiliitis grade G≥1 (minimum lesion) bilaterally or G≥2 (moderate lesion) unilaterally; 2) without large or deep erosions(d≥1cm) in neither iliac nor sacral side; 3) if the spine is involved, the syndesmophytes are thin and smooth on consecutive vertebrae. We also discussed differential diagnosis with other easily confused diseases, such as psoriatic arthritis, and diffuse idiopathic skeletal hyperostosis. As part for this work, we summarized detailed points of skeletal pathological manifestations to be recorded in the diagnostic process.
Reviewing 30 paleopathological or archaeological studies in China we found that since the Holocene, 128 human skeletons have been identified as AS. However, only 25.8% (n=33) met our new diagnostic criteria after being reanalyzed. The remaining 74.2% of cases were diagnosed with AS based on “spinal fusion” on only two vertebrae or lacking pathological information of the sacroiliac joint, which could not be well distinguished from other diseases. These suspected cases need further investigation.
Among these 33 confirmed cases, 63.6% (n=21) were males. There were 27 individuals with definite age range of death, mainly middle-aged individuals (n=17). The earliest cases dated back to the Neolithic Age (n=4), then the Xia, Shang and Zhou dynasties (n=5), the Warring States, Qin and Han dynasties (n=13), the Wei, Jin, Southern and Northern dynasties (n=8), the Sui and Song dynasties (n=1), and the Yuan and Qing dynasties (n=2). Almost all cases were located north of the Yangtze River, possibly an influence of bone preservation.
The aim of this study is to create a process for recording and diagnosing ancient AS more standardized and normalized, leading to more accurate and persuasive identification results. This work established a solid foundation in study of the developmental and evolutionary history of AS. In addition to morphological diagnosis, the HLA-B27 test is another important means to diagnose AS. The advent of ancient DNA techniques has brought forth potential molecular means of diagnosis and investigation of this hereditary disease especially for mutilated skeletal remains.