General radiological and prenatal features
On radiographs of patients with this pathology, bones may retain normal length or become shortened, thickened, and deformed as a result of multiple fractures. Specific radiological findings include insufficiency fractures (insufficiency fractures), hypertrophic callus formation (hypertrophic callus), and ossification of interosseous ligaments. When examining the skull, a classic sign is the presence of Wormian, or sutural, bones (Wormian bones).
Severe forms of the disease are amenable to prenatal diagnosis as early as the second trimester of pregnancy using detailed ultrasound or fetal magnetic resonance imaging. Key intrauterine signs include:
- Shortening and bowing of the limbs caused by intrauterine fractures.
- Relative macrocephaly with a prominently protruding forehead (frontal bossing).
- Flat midface (flat midface).
In types III and VII (the latter being recessive and associated with a CRTAP gene mutation), intrauterine and perinatal fractures lead to the most pronounced skeletal deformations.
Type I: most frequent and mildest form
The first type of the disease is the most common and mildest form, which is inherited in an autosomal dominant manner (autosomal dominant). Often the pathology becomes obvious only in adulthood, but history-taking reveals that fractures occurred from early childhood. Clinically and radiologically, the peak of trauma occurs when the child transitions to a more active lifestyle (older than five years). Both overt fractures and microfractures affecting bone metaphyses occur.
In infancy, the clinical picture may mistakenly resemble non-accidental injury (non-accidental injury). Bone biopsy is rarely used to confirm the diagnosis; as a rule, studying the family history and searching for characteristic extraskeletal manifestations is sufficient. These include:
- Blue sclerae (blue sclerae).
- Dentinogenesis imperfecta (dentinogenesis imperfecta).
- Marked joint hypermobility (joint laxity).
- Presenile (early) hearing loss (presenile hearing loss).
The majority of such patients are short in stature — only 10% reach normal parameters. Radiographs show a decrease in radiodensity (radiodensity), and the bones themselves may appear gracile (gracile), although sometimes modeling and density remain normal. In the fourth decade of life, especially in the presence of scoliosis, vertebral fractures frequently develop.
Type II: lethal perinatal form
The second type represents an extremely severe pathology incompatible with life. Infants are born small for gestational age (small for dates). They exhibit deep blue sclerae (deep blue sclerae) and deformations of shortened limbs due to sustained fractures.
Death occurs in the first months of life (survival past three months is extremely rare) as a result of pulmonary insufficiency (pulmonary insufficiency) triggered by rib fractures. Severe complications include concomitant brain and spinal cord injuries.
Characteristic radiological picture of type II:
- Lower extremities: a specific 'concertina' deformity develops ('concertina' deformity).
- Ribs: acquire a 'beaded' appearance ('beaded') due to multiple intrauterine fractures.
- Skull: the vault is under-mineralised (under-mineralised) and frequently deformed during passage through the birth canal (moulding). Wormian bones are present in the occipital and parietal regions.
- Spine: platyspondyly (platyspondyly) — flattening of the vertebral bodies — is observed.
Histologically, this type reveals a defect of endochondral ossification (endochondral ossification) in the metaphyses and epiphyses. Bone tissue appears disorganized, containing persistent islands of calcified cartilage and areas of hypomineralized bone.
Briefly: answers to topical questions
What genetic mutations are associated with severe intrauterine forms of osteogenesis imperfecta?
Severe intrauterine and perinatal forms of osteogenesis imperfecta are associated with mutations in several genes that determine the type of the disease.
- Type II (Lethal Perinatal) — mutations in COL1A1, COL1A2, CRTAP, LEPRE1, PPIB genes.
- Type III — mutations in the same genes as in type II, as well as FKBP10, SERPINH1.
- Type VII — mutation of the CRTAP gene.
What inheritance patterns exist for the various forms of osteogenesis imperfecta?
Autosomal dominant (AD) and autosomal recessive (AR) inheritance patterns occur in various forms of osteogenesis imperfecta.
| Disease type | Inheritance pattern |
|---|---|
| Type I | AD (autosomal dominant) |
| Type II | BP, AR |
| Type III | BP, AR |
| Type IV | BP, AR |
| Type V | BP |
| Type VII | Recessive |
In overall monogenic disease statistics, the disorder is classified as autosomal dominant.
To remember the typical extraskeletal manifestations of the first type, use the rule of four H's (or in Russian, four S's): Hearing (early loss), Joints (hypermobility), Sclerae (blue), and Skeleton/teeth (dentinogenesis imperfecta).
Class and exam questions
What conditions must type I osteogenesis imperfecta in infants be differentiated from?
In infancy, frequent fractures can be mistaken for non-accidental injury. The diagnosis is confirmed by the presence of specific extraskeletal manifestations (blue sclerae, early hearing loss) and a burdened family history.
What are the main causes of death in type II of the disease?
Death of newborns with type II osteogenesis imperfecta usually results from pulmonary insufficiency caused by multiple severe rib fractures.
When and how can severe forms of the pathology be detected intrauterinely?
Diagnosis of severe forms is possible as early as the second trimester of pregnancy via detailed ultrasound and/or fetal MRI, which reveals limb shortening and skull deformations.
What else to study on this topic
- Mechanisms of formation of Wormian (sutural) skull bones
- Pathogenetic features and the CRTAP gene mutation in type VII
- Histological defects of endochondral ossification in type II
- Relationship between platyspondyly and the development of scoliosis
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