Leprosy in skeletons from archaeological sites: A systematic review

Leprosy (Hansen's disease) is an ancient stigmatising infectious disease that remains endemic in many countries. Leprosy-related bone changes that cause disabilities in affected persons are evident in skeletons from archaeological sites. The aim of our synthesis of paleopathological data was to gain insights into the disease's historical distribution and presentation.

Systematic review of paleopathological studies describing human remains with signs of leprosy published up to December 2023. Extracted data on bone features from skulls and limbs, including rhinomaxillary syndrome (RMS) in cranial bones and post-cranial bone changes (PCBC) in hands and feet, were summarised, together with genomic data from studies of Mycobacterium leprae ancient DNA.

The 297 skeletons described in 67 studies comprised 264 skeletons from sites in modern-day Europe (117 from England, 68 from Denmark); 23 skeletons from Asia (10 from India), 5 from The Americas, and 4 from the African continent (all from Egypt); 174 (58.6%) were from leprosaria, 255 (85.9%) were adults, 28 (9.4%) adolescent, 14 (4.7%) of indeterminate age. Skeletons dated from 3715 BCE to 1839 CE, peaking around the 15th Century. Probable and possible RMS were identified in 85 (30.5%) and 153 (54.8%) of 279 skeletons with cranial data, respectively. Lower limb pathological PCBC were most prevalent in tarsals (76.6%), metatarsals (81.5%), and feet phalanges (85.6%). In upper limbs, 75.8% of humeri, 65.8% of radii, 61.0% of ulnae and 75.8% of hand phalanges exhibited pathological alterations. From 73 skeletons from 19 genomic studies, M. leprae single nucleotide polymorphism (SNP) type 3 was identified in 59 skeletons (80.8%), SNP type 2 in 11 (15.1%), type 4 in two, and type 1 in one.

Four out of five archaeological skeletons with leprosy exhibited some degree of RMS, which is pathognomonic of the most severe form of the disease, irrespective of whether the skeleton was excavated from a leprosarium (leprosy hospital) or from a public cemetery or other burial site. The relatively small numbers of remains excavated over a wide geographical area and a long time period, and the focus of archaeological studies on skeletons already identified as having leprosy, mean that it is difficult to prove or disprove theories that aim to explain the decline and eventual disappearance of leprosy as a disease in Europe.