Paleopathology II: disease and abnormalities

Disease

Disease is an abnormal condition or disorder of a body structure or function. Some diseases, such as certain metabolic syndromes (discussed in Chapter 5), cancer, or autoimmune conditions, originate from some internal condition or defect. Others, such as bacterial or viral infections, primarily originate outside the body and can spread from person to person (contagious diseases). Disease is viewed as a medical condition associated with specific indications, and the study of disease is called pathology.

Pathology of disease addresses four components: (1) etiology (cause), (2) pathogenesis (mechanisms of development), (3) morphologic change (structural alterations of cells), and (4) clinical manifestations (the consequences of changes). Paleopathology of disease involves scientific research to increase accuracy in diagnosis in ancient human remains and to place disease within a biocultural context (e.g., Waldron 2009). The effects of disease on morbidity and mortality are poorly known (except in some cases such as the bubonic plague in Europe). For example, nonvenereal syphilis diseases often leave skeletal markers in their late stages but are not commonly fatal, whereas tuberculosis is rarely seen in skeletal remains but has a high risk of death, perhaps leading to an underestimation of the impact of tuberculosis on mortality (Cook and Powell 2006:311).

Epidemiology is the study and analysis of the patterns, causes, and effects of health and disease conditions in defined modern populations. Paleoepidemiology focuses on the same issues in past populations and is an integral part of understanding the impact of disease on those populations (e.g., Milner and Boldsen 2017).

Skeletal pathology of disease

The majority' of skeletal pathologies result from infectious, degenerative, and nutritional deficiency diseases, with pathology related to degenerative disease the most common (White and Folkens 2005:312). Trauma, although not technically a pathology, is also often evident on skeletal remains and is considered in Chapter 7. Comprehensive reviews of human skeletal pathologies are present in White and Folkens (2005), Roberts and Manchester (2007), Waldron (2009), Mann and Hunt (2012), Larsen (2015), and Buikstra (2019). Dental pathology is discussed separately later.

Most diseases are too short-lived to form distinct lesions on the skeleton, although such evidence is sometimes present (e.g., Roberts and Manchester 2007; Waldron 2009)

(Table 6.1). However, some chronic conditions can result in the formation of lesions on the surface of the bone, but such lesions are usually nonspecific (Rothschild and Rothschild 1997) and poorly understood (Lewis 2004). A few diseases will produce diagnostic bone lesions that can be identified in individuals and populations. A relatively new approach to the identification of disease in bone is the detection of specific pathogens using ancient DNA (aDNA) (e.g., Rasmussen et al. 2015; Nieves-Colon and Stone 2019:530-533).

Table 6.1 Some diseases and corresponding general pathologies

Infections of the bone can occur on the surface or interior of the bone. If the periosteum — the tissue on the surface of the bone - becomes infected, it results in a periosteal reaction (or periostosis), frequently forming a lesion (Waldron 2009:84) (Figure 6.1). Periostosis is often the result of a trauma or other stimuli of the periosteum (see Waldron [2009:Table 6.71 for a list of some possibilities), typically results in the formation of new bone, and is most often identified on radiographs. New bone formation would indicate an infection or trauma but may not reveal a specific cause, and in subadults “should be regarded as physiological until proved otherwise” (Waldron 2009:116). Periosteal reactions on the interior surfaces of the ribs can be an indicator of lower respiratory tract disease (Davies-Barrett et al. 2019).

Figure 6.1 A periosteal lesion on a left tibia Source: Eric Bartelink

If the interior of the bone becomes infected, it is called osteomyelitis. Such an infection could be the result of a penetrating injury (such as an animal bite or compound fracture), the direct spread of an infection from an adjacent (e.g., periosteal) area, or the indirect spread of an infection from another area via the bloodstream (Waldron 2009:84). Osteomyelitis infections result in the formation of a great deal of pus within the bone, causing internal pressure that may alter the shape of the bone and/or result in the formation of cloacae (drainage channels that appear to be foramina [openings in the bone for nerves or blood vessels]). In addition, new bone can form over the infected area in an attempt to “repair” the damage. Ear infections can involve the mastoid process, called mastoiditis, and can cause deafness (Flohr and Schultz 2009).