Hereditary and congenital bone and joint diseases

Bone and joint dysplasias are hereditary and congenital diseases of heterogeneous cause that affect both structure and function. Examples of this group of diseases include Marfan syndrome, Ehlers–Danlos syndrome and osteogenesis imperfecta, among many others.

Which tissue is predominantly affected depends on the disrupted structure of the proteins or substances that are poorly synthesised because of the congenital disease. Hereditary and metabolic bone and joint diseases can present in the bones, cartilage, tendons, ligaments and muscles, but also in seemingly unrelated organs such as the eyes, skin, teeth, heart, blood vessels and lungs.

Osteogenesis imperfecta is caused by a defect in type I collagen. Clinically, it presents with brittle bones, blue sclerae and abnormal development and appearance of the teeth.

Ehlers–Danlos syndrome is caused by a genetic disorder of the extracellular matrix. It presents with joint hypermobility, skin hyperextensibility and tissue fragility.

Marfan syndrome is caused by a deficiency of fibrillin-1. Clinically, it presents with a typical marfanoid habitus, an ectopic lens of the eye and dilatation of the aortic arch. The marfanoid habitus, or Marfan syndrome, is typical of tall, thin people with disproportionately long limbs, chest deformities, scoliosis, thoracic lordosis, limited elbow extension, flat feet, hip deformities and increased joint mobility. Changes in the shape of the head – dolichocephaly (an elongated head), enophthalmos (sunken eyeballs), retrognathia (a receding lower jaw) – as well as crowded teeth and a gothic (high-arched) palate are also typical features of this syndrome.