Know Your Pathology: Leprosy

Leprosy, also known as Hansen’s disease, is “a chronic infectious disease of humans, affecting skin, nasal tissues, peripheral nerves and bones caused by Mycobacterium leprae” (Aufderheide and Rodríguez-Martín, 1998: 141). Co-existing with tuberculosis in many regions of the world today, the leprosy bacilli are transmitted either by inhalation or by direct contact into an open wound from an infected individual. Unlike tuberculosis, however, leprosy is not readily communicable. Those who acquire the condition have frequently been in prolonged contact with infected individuals (Larsen, 1997: 104). This perhaps explains the fact that today this is a disease with high rural incidence, clustering in families (Manchester and Roberts, 1989: 267).

Neurotrophic changes are commonly seen in advanced leprosy. Destruction of the sensory nerves with ensuing anaesthesia and circulatory alterations lead to slowly progressive atrophy of terminal phalanges, resorption progressing proximally, even as far as the metapodials in some instances. Severe degenerative arthritis and neuropathic arthropathy, similar to Charcot’s joint, can be seen in weight-bearing joints such as ankles and feet. In addition, the existing anaesthesia facilitates traumatic mutilations and secondary infections  (Ortner and Putschar, 1981: 177). Such paralysis also predisposes the individual to fractures caused by clumsiness or uncoordination (Judd and Roberts, 1998: 53).

If the affected individual has good immunological resistance the disease is confined to the nerves, producing what is known as the tuberculoid form of the disease. If resistance is poor then the lepromatous form occurs. Borderline cases can, and do, occur, however. Skeletal changes occur in both forms, but they are more frequent in the lepromatous form (Waldron, 2001: 101). Disruption of the muscles in the lower limbs and hands, as well as paralysis of the ulnar nerves, results in claw-hand deformities. Whilst such paralysis can be difficult to determine in archaeological specimens, in at least one instance a groove has been identified on the volar surface of the distal end of the proximal phalanx, a lesion also noted in the radiographs of modern patients (Andersen and Manchester, 1987: 78). Similar loss of motor function in the feet leads to the collapse of the longitudinal arch and the development of pes planus, or flat foot. The tensile stress this imparts to the ligaments is likely to be the cause of exostoses found at the sites of attachment (Andersen and Manchester, 1988: 52-54).

Facies leprosa of the skull shows atrophy of the anterior nasal spine, in most cases combined with central atrophy of the alveolar process. This is classified into three degrees (Møller-Christensen and Inkster, 1965: 11):

I° – in which there is a well-defined reduction of the spine;
II°- in which there is an advanced nasal spine atrophy although a distinct but very small nasal spine remains;
III° – in which there is a complete obliteration of the nasal spine.

The atrophy of the maxillary alveolar process and inflammatory changes of the superior surface of the hard palate are also classified into three degrees in a similar manner (Møller-Christensen and Inkster, 1965: 11). Further bone changes are set out in Møller-Christensen (1961).

The deformations associated with advanced leprosy led to sufferers being segregated, especially during the medieval period with theologians portraying the disease as the chastisement of God. The concept of the leper hospital did not really develop until the eleventh century AD, the third Lateran Council issuing orders for the isolation of lepers in 1179 (Rawcliffe, 1995: 14), at which point there was a sudden explosion in the numbers of these institutions. This suggests that either leprosy was becoming more common, that disease generally was becoming more common, or that society was becoming more charitable (Manchester and Roberts, 1989: 268). Alternatively, it may be viewed as part of a wider crusade against heretics, Jews, homosexuals, and anyone else whose behaviour was viewed as suspicious (Rawcliffe, 1995: 14).

The cross-immunity of leprosy and tuberculosis may explain the decline in leprosy towards the fourteenth century when there is a coincident rise in tuberculosis (Manchester and Roberts, 1989: 269). This relationship is not simple, nor universal, and appears to be affected by multiple variables. However, it may be this that explains the burial of two leprous males and tuberculous female from the Iron Age of South East Asia (Tayles and Buckley, 2004: 253).

A study aimed primarily at the epidemiological analysis of leprosy in medieval Denmark devised a simple recording form that allowed them to generate large amounts of data relatively quickly. In this the osteological changes were recorded in seven locations (Boldsen, 2001: 383):

  1. the edge of the nasal aperture;
  2. the anterior nasal spine;
  3. the alveolar process on the premaxilla;
  4. the palate;
  5. subperiosteal exostoses on the fibula;
  6. porotic hyperostosis on the fibula;
  7. the fifth metatarsal

Whilst it is acknowledged that some symptoms are best described as a multi-stage sequence of events, for the sake of simplicity all were recorded simply as 1) present or 2) absent. Zero indicated the condition was unobservable in that skeletal element. This coding could then be analysed using statistical packages to describe the frequency and prevalence of the disease (Boldsen, 2001: 383). Such simplicity does make this recording system easy to apply, and also easy to duplicate by other researchers. Scoring changes merely as present or absent reduces the likelihood of inter-observer error, which, on the whole, is more likely to arise with examples of minor change. It does, however, possibly over-simplify the sequence of many of the symptoms, and has the effect of grouping together all sufferers with the condition regardless of the degree of advancement. This could mean that some more subtle nuances of patterning are lost.

Many skeletal changes are considered characteristic of leprosy, however, others such as tibial periostitis may be caused by several different infections. The identification of Mycobacterium leprae DNA can, therefore, be very useful in confirming a diagnosis (Wilson, 1999: 14), and this is an approach that is becoming more common as the techniques involved in the study of ancient DNA improve. An example of this is a case from Byzantine Israel where the presence of M. lepra was used to differentiate between leprosy and a condition known as Madura foot, or Mycetoma (Spigelman and Donoghue, 2001).

Palaeohistopathological analysis can help to differentiate diseases such as leprosy from other specific infections like treponemal disease and from non-specific conditions. For example in lepromatous periostitis polster-like structures that are rudimentarily developed and relatively flat can be observed, in contrast to those of treponematosis which tend to be well-developed (Schultz, 2001: 126). Furthermore, in contrast to chronic treponemal disease, there are no observable grenzstreifen in chronic leprosy (Schultz, 2001: 128).

References:

Andersen, J. G and Manchester, K. 1987. Grooving of the proximal phalanx in leprosy: a palaeopathological and radiological study. Journal of Archaeological Science 14: 77-82.

Andersen, J. G and Manchester, K. 1988. Dorsal tarsal exostoses in leprosy: a palaeopathological and radiological study. Journal of Archaeological Science 15: 51-56.

Aufderheide, A. C and Rodríguez-Martín, C. 1998. The Cambridge Encyclopedia of Human Paleopathology. Cambridge: Cambridge University Press.

Boldsen, J.L. 2001. Epidemiological approach to the paleopathological diagnosis of leprosy. American Journal of Physical Anthropology 115: 380-387.

Judd, M. A, and Roberts, C. A. 1998. Fracture patterns at the medieval leper hospital in Chichester. American Journal of Physical Anthropology 105: 43-55.

Larsen, C. S. 1997. Bioarchaeology: Interpreting behavior from the human skeleton. Cambridge: Cambridge University Press.

Manchester, K, and Roberts, C. 1989. The palaeopathology of leprosy in Britain: a review. World Archaeology 21 (2): 265-272.

Møller-Christensen, V. 1961. Bone Changes In Leprosy. Bristol: John Wright & Son Limited.

Møller-Christensen, V, and Inkster, R.G. 1965. Cases of leprosy and syphilis in the osteological collection of the Department of Anatomy, University of Edinburgh. Danish Medical Bulletin 12 (1): 11-18.

Ortner, D. J, and Putschar, W. G. J. 1981. Identification of Pathological Conditions in Human Skeletal Remains. Smithsonian Contributions to Anthropology 28. Washington and London: Smithsonian Institution Press.

Rawcliffe, C. 1995. Medicine and Society in Later Medieval England. Stroud: Sutton Publishing.

Schultz, M. 2001. Paleohistopathology of bone: a new approach to the study of ancient diseases. Yearbook of Physical Anthropology 44: 106-147.

Spigelman, M and Donoghue, H. D. 2001. Brief communication: unusual pathological condition in the lower extremities of a skeleton from ancient Israel. American Journal of Physical Anthropology 114: 92-93.

Tayles, N and Buckley, H. R. 2004. Leprosy and tuberculosis in Iron Age Southeast Asia? American Journal of Physical Anthropology 125: 239-256.

Waldron, T. 2001. Shadows in the Soil: Human Bones and Archaeology. Stroud: Tempus Publishing.

Wilson, L. E. 1999. Leprosy in Scotland. Unpublished MA dissertation. University of Leicester.

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One response to “Know Your Pathology: Leprosy

  1. Pingback: Know Your Pathology: Treponematosis « Archaeozoology

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