Osteogenesis Imperfecta, Type II

Alternative Names

  • OI, Type II
  • OI2
  • OIC
  • Osteogenesis Imperfecta Congenita
  • Osteogenesis Imperfecta Congenita, Perinatal Lethal Form
  • Vrolik Type of Osteogenesis Imperfecta
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WHO-ICD-10 version:2010

Congenital malformations, deformations and chromosomal abnormalities

Congenital malformations and deformations of the musculoskeletal system

OMIM Number

166210

Mode of Inheritance

Autosomal dominant

Gene Map Locus

7q21.3,17q21.33

Description

Osteogenesis imperfecta is a group of rare connective tissue disorders characterized by increased bone fragility and low bone mass. Affected individuals present a broad range of clinical severity, ranging from multiple fracturing in utero or perinatal death to normal adult stature and a low fracture incidence. The disorder is currently classified into seven types based on differences in clinical presentation and bone architecture. Osteogenesis imperfecta type I is the most common and the mildest form of the disorder.

Osteogenesis imperfecta congenita or type II osteogenesis imperfecta is the most severe form of the disease. Patients exhibit short limb dwarfism, thin skin, soft skull, unusually large fontanels (soft spots), blue sclera, whites of the eyes, small nose, low nasal bridge, inguinal hernia and numerous bone fractures at birth. There is bowing of limbs due to multiple fractures. More than 60% of affected infants die on the first day; and 80% die within the first week. Survival beyond the first year is exceedingly rare and usually involves intensive support such as continuous assisted ventilation. Death usually results from pulmonary insufficiency related to the small thorax, rib fractures, or flail chest due to lack of stable ribs.

Osteogenesis imperfecta is an autosomal dominant disorder caused by mutations in type I collagen genes - COL1A1 and COL1A2. COL1A1 and COL1A2 encode the alpha 1 and alpha 2 chains of the collagen triple helix, respectively. More than 250 different mutations in the COL1A1 and COL1A2 genes had been characterized. These alterations vary in type and location. The mild forms of osteogenesis imperfecta are usually caused by mutations that inactivate one allele of the COL1A1 gene, resulting in a reduced amount of normal type I collagen. The varied clinical characteristics of osteogenesis imperfecta reflect different classes of mutations in different regions of type I collagen genes.

Epidemiology in the Arab World

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Other Reports

Arab

In a 5-year prospective study for newborns at Al Ain Medical District, Al-Gazali et al. (2003) defined the pattern and birth prevalence of the different types of osteochondrodysplasias in the United Arab Emirates. Among the 38,048 births during the study period, 36 (9.46/10,000 births) had some type of skeletal dysplasia of which two, born to non-consanguineous parents, had osteogenesis imperfecta type II (0.52/10,000 births). Al-Gazali et al. (2003) noted that the birth prevalence of osteogenesis imperfecta is higher in the UAE population than those reported for other populations (0.24-0.37/10,000).

Algeria

Kaplan and Baldino (1953) described a kindred derived from an inbred, Arabic-speaking, polygamous sect called the Mozabites, living in southern Algeria. Nine cases occurred in 4 sibships among the descendants. Kaplan et al. (1958) and Laplane et al. (1959), in a follow-up of the same kindred, described 19 cases.

Lebanon

Bittar (1998) reported a prospective study of 3,865 consecutive newborns delivered between 1991 and 1993. Major congenital anomalies (MCA) were found in 64 newborns at incidence of 16.5/1000 births. Many of the cases had osteogenesis imperfecta. Among the malformed infants, the rate of low birth weight and the rate of parental first cousin consanguinity were significantly higher than corresponding rates among normal infants in a control group.

Oman

Sawardekar (2005) conducted a study to establish the prevalence of major congenital malformations in children born during a 10-year period in Nizwa Hospital. Of the 21,988 total births in the hospital, five children were born with osteogenesis imperfecta type 2. Sawardekar (2005) hinted for a possible genetic contribution in these children.

Sudan

Doumi et al. (1994) reported a prospective study of fractures in 231 children received at Khartoum North Teaching Hospital (KNTH). The incidence of child fracture rated as one per day and it increased from the age of 5 years onwards in boys and between 6 and 8 years in girls. Pathological fractures accounted for 2.2% and were due to bone cysts and osteogenesis imperfecta.

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