Osteogenesis Imperfecta

At a glance

Group of rare disorders affecting the connective tissue and characterized by extremely fragile bones that break or fracture easily during the antenatal and postnatal periods (brittle bones). The severity of osteogenesis imperfecta varies greatly, even among individuals of the same family. Four main types have been identified. Type I is the most common and the mildest form of the disorder. Type II is the most severe form. The term osteogenesis imperfecta congenita refers to the more severe condition.

Synonyms

Brittle Bone Disease; Ekman-Lobstein Syndrome; Lobstein Disease; Fragilitas Ossium; Blue Sclera Disease, Porak-Durante Disease; Osteogenesis Imperfecta Tarda; Osteogenesis Imperfecta Congenita; Neonatal Lethal Form Osteogenesis Imperfecta; Vrolik Osteogenesis Imperfecta Syndrome; Glass Bone Disease, Bruck Syndrome.

History

The term “osteogenesis imperfecta” came into use in 1895, and it means imperfect bone formation. Osteogenesis imperfect is known since ancient history.

Incidence

This medical condition affects about 1 in 15,000 people.

Genetic inheritance

Autosomal dominant and autosomal recessive.

Classification

Two classifications are currently available: Sillence and Forlino.

• Sillence Classification: There are four main types of osteogenesis imperfecta in the Sillence description with at least a further 12 types added. Subdivision Types A and B are based on the absence or the presence of dentinogenesis imperfecta within each condition.

  • Type I (Osteogenesis Imperfecta Tarda; Osteogenesis Imperfecta with Blue Sclerae): Dominantly inherited, generalized connective tissue disorder characterized mainly by bone fragility and blue sclerae.

  • Type II (Osteogenesis Imperfecta Congenita; Neonatal Lethal Form Osteogenesis Imperfecta; Vrolik Osteogenesis Imperfecta Syndrome): Autosomal dominant characterized by spontaneous fractures, generalized osteoporosis, and wormian bones in the area of the lambdoidal sutures. Blue sclerae and deafness are not present. Mucoid changes in the connective tissue of the heart valves and aorta lead to congestive heart failure and death.

  • Type III (Osteogenesis Imperfecta Progressively Deforming with Normal Sclerae): Believed to be about one-eighth as frequent as dominantly inherited osteogenesis imperfecta with blue sclerae. In this type, dentinogenesis imperfecta is particularly striking, especially in the primary dentition. Severe kyphoscoliosis and multiple limb deformities are reported.

  • Type IV (Osteogenesis Imperfecta with Normal Sclerae): Autosomal dominant characterized by short stature, often below fifth percentile, hearing loss and otosclerosis, normal-grayish sclerae, and presence of dentinogenesis imperfecta. The skull presents wormian bones. Onset is in the newborn period, with fractures occurring in utero, during labor and delivery, or shortly after birth.

• Forlino Classification: The Forlino classification recognizes the identification of autosomal recessive forms and an understanding of osteogenesis imperfecta with collagen defects and is separating five groups A to E:

  • Group A: Defects in collagen synthesis, structure, or processing. This group includes Types I to IV as above and the autosomal recessive Type XIII (mutation in BMP1 gene on location 8p21.3)

  • Group B: Defects ...