Biology Reference
In-Depth Information
ankylosing spondylitis versus DISH,
6
treponemal disease: yaws versus bejel
7
). However,
under certain contextual circumstances (based on information from archaeology or ecology),
the causes or factors can be differentially weighed. With respect to similarly presenting
diseases, there may be particular reactive changes that distinguish one from another. In order
to identify a particular pathology or mediating factor, the scholar must therefore be aware of
the total range of bone change associated with the progress of that pathology and the other
disease processes that might mimic such responses (i.e., differential diagnosis).
This does not mean that other reactive responses are not possible. Other, and likely ever-
present, stress circumstances (e.g., malnutrition, osteoporosis, or endemic disease process)
may impact a particular pathology (i.e., a synergistic response) that could complicate the
bone's repair process. Therefore, the scholar should fully describe all the changes and
their distribution throughout the skeleton because (1) pathologies may interact synergisti-
cally, (2) detail would help discriminate between pathologies and support a particular
differential diagnosis, and (3) potentially disease-discriminating minor changes may exist
which might previously have been overlooked. However, in the end, a diagnosis is always
a probability statement and the prudent scholar always considers (and reports) alternative
identifications.
There is a set vocabulary utilized in differential diagnosis that the scholar should know
and utilize. If reactive changes are categorized as pathognomonic (often misspelled as “path-
ognomic”), they are unique to the disease described and reflect the highest level of diagnostic
confidence. Pathological indicators that are labeled diagnostic also indicate a high level of
diagnostic confidence, but the reactive changes may not be exclusive to the disease process.
If a reactive change is labeled as “consistent with” or a similar descriptor (e.g., “indicative”),
the changes are generic but the particular disease cannot be diagnostically excluded. This
final category is useful if a disease process has been identified in a given archaeological
sample by pathognomonic or diagnostic cases and other cases are suspected. Adjectives
for “consistent with” are often metaphorically used (e.g., “probable,” “possible”) to suggest
the confidence with which pathological cases are diagnosed. In many osteological samples,
most cases fall into the “consistent with” category. This does not necessarily reflect the diag-
nostic shortcomings of the observer. Rather, it reflects the inherent complexity of disease
progress in individuals who differ in vulnerability (i.e., frailty) and the significant overlap
in reactive changes (
Weston, 2008
). It also emphasizes the analytical utility of the category
of nonspecific infection to suggest stress.
6
Ankylosing spondylitis (AS) and diffuse idiopathic skeletal hyperostosis (DISH) describe bone
overgrowth of the ligamentous sheaths of vertebral bodies. Ideally they can be distinguished by the
predilection of location and pattern of reactive change. That is, AS is described as “bamboo-spine” and
DISH is often described as resembling “dripping candle wax.” Many particularly advanced cases when
overgrowth is morphologically complex and bilateral on the vertebral body are difficult to distinguish. This
can be particularly problematic in archaeological contexts as cases may be incomplete or poorly preserved.
See Rogers et al. (1985), Aufderheide and Rodr
´
guez-Mart
´
n (1998:96
e
105), and Ortner (2003:558
e
560,
571
e
577).
7
Osteologically indistinguishable syndromes of an endemic pre-Columbian disease. See
Cook and Powell
(2005)
.
