Osteogenesis Imperfecta (OI), more commonly known as ‘brittle bone’ disease is a condition which causes bones to be fragile and break easily. I have a personal interest in this condition and therefore wondered if there was any evidence of the condition in the archaeological record. A quick search produced this article ‘Osteogenesis Imperfecta in the Archaeological Record: An Example from the Dakhleh Oasis, Egypt,’ by Cope & Dupras (2011).
OI results from a genetic mutation that affects the production of collagen in the body. Collagen, along with calcium, provides strength and flexibility in bones with collagen providing flexibility. When this is removed bones become brittle and therefore will fracture easily. You can see this for yourself by baking a bone, as this removes the collagen, follow this link if you want to try if yourself. In the case of OI a genetic mutation diminishes the production of collagen resulting in multiple fractures and breaks. The majority of individuals with the condition receive it through a dominant mutation, whilst a small portion have an autosomal recessive condition. There are seven categories of OI with type I being the mildest form. I will summarise the different types below but there is also a more extensive table describing the categories on page 189 of the article.
- Type I: mildest, high risk of fractures, subsides at puberty, individual reaches normal height.
- Type II: typicallystill born due to a respiratory complications
- Type III: likely to die shortly after birth as a result of respirority faliure.
- Type IV: short stature (smaller than type I), bone fragility not identified at birth. Progressive bowing of bones.
- Type V: similar to type IV but possible calcification of interosseous membranes of forearms and hyperplastic calluses of bone.
- Type VI and VII: Rare. Scale-like structure to lamella with type VI having an increase in osteoid thickness and VII with a shortening of femora and humeri.
The article ‘Osteogenesis Imperfecta in the Archaeological Record: An Example from the Dakhleh Oasis, Egypt’ proposes that a fetal skeleton, B532 excavated in a cemetery in Egypt, may have OI. The cemetery dates from the Ptolemaic to the Romano-Byzantine period and the grave itself was found in unusual position. Typical juvenile burials of this at this site were orientated East-West in a supine, extended position (how we usually think of a body when it is buried). However, this individual was recovered close to the surface lying partially on it’s back and right side in a semi-flexed position. The skeleton was in excellent condition due to the arid environment resulting in exceptional preservation and was given an estimate age of 36 – 42 weeks.
A full pathological assessment of B532 was completed with a summary provided in table 2, p. 194 of the article. The most prominent pathology of this individual was the severe curvature of the long bones and barrel-shaped rib cage. This barrel-shape is a result in abnormal curvature and thinness of the ribs. The curve in the long bones was predominately anterolateral (to the front and to the side) with the femora having the most extensive. In addition to the curves visible in the long bones the left femur, tibia and ulna also had fractures. These were complete in the ulna and tibia and partial in the femur.
The cortical bone was also had an unusual appearance which was coarse and patchy. This was observed in the left humerus and the right ulna and radius. The medullary cavity of these bones, plus the other humerus, was also narrowed. Both of these features are unusual and indicate a problem in the development of the bone. Microscopic analysis of type II OI has found that due to a disorganised osteoid and calcified bone matrix patchy bone mineralization can occur. In addition to this when using a light and electron microscope to examine type II OI sample an absence of mineralization at the distal ends of the growth plates was observed; instead starting further down the diaphysis. This lack of mineralization may account for the uneven surface seen in B532, and when combined with the observed fractures and curvature of the long bones indicates a possible diagnosis of OI, type II/III or IV.
In all pathological cases a differential diagnosis is also given for comparison. In this individual many diagnoses were given which may also account for the bowing seen in B532. A full list is given in table 3, p.196 and includes Campomelic Dysplasia 1, a condition which results in bowing of the long bones and hypoplastic fibulae and scapulars caused by abnormal skeletal development during the prenatal period.
This was a very interesting case study of a fetal skeleton who possibly suffered with the condition Osteogenesis Imperfecta. The article is a good example of a through approach to diagnosing pathology in an excavated skeleton. This is not the only example of OI in the archaeological record and I intend to go away and find out more about the other cases.
Cope, D. & Dupras, T. (2011).’ Osteogenesis Imperfecta in the Archaeological Record: An Example from the Dakhleh Oasis, Egypt,’ by Cope & Dupras’ in International Journal of Paleopathology 1: 188-199. ISSN 1879-9817, http://dx.doi.org/10.1016/j.ijpp.2012.02.001. (http://www.sciencedirect.com/science/article/pii/S1879981712000022)