Other names:
1. Brittle Bones
2. Fragilitas Ossium
3. Osteopsathyrosis
4. Lobstein's disease
Definition:
Osteogenesis imperfecta is heterogenous group of genetic diseases (predominantly autosomal dominant, occasionally autosomal recessive) which is due to abnormal type I collagen (a collagen present in tissues such as bones, sclera, tendon, dentin and skin) that results in widespread defect in these tissues.
Etiology:
Mutation of genes coding for type I collagen particularly
- COL1A1 located in chromosome 17q21
- COL1A2 located in chromosome 7q22.1
Classification of Osteogenesis Imperfecta: (Put Pic)
1. Type I: Mildest and most common
2. Type II: Most severe : most prenatal fractures and 90% - 4 weeks after postnatal life
3. Type III: 50% prenatal and 50% in utero fractures
4. Type IV: fractures begin in infancy
Clinical Features:
1. Extreme fragility and porosity of bone, with proneness to fracture
2. Pale blue sclera
4. Laxity of ligaments leading to hypermobility of joints
5. Tendency to capillary bleeding
Oral Manifestations:
1. Class III malocclusions (due to maxillary hypoplasia)
2. Anterior and posterior crossbites and open bites
3. Impactions, ectopic teeth, unerupted first and second molars
4. Abnormal dentin formation termed as Opalescent dentin and is
similar to dentinogenesis imperfecta (since type I collagen is a major constituent)
Radiographic Features:
1. Osteopenia
2. Bowing and angulation of long bones
3. Multiple fractures
4. Multiple Wormian bones
5. Multiple radiolucencies, radiopacities or mixed radiolucencies of the jaw bones in panoramic radiographs
6. Premature pulpal obliteration of affected teeth in periapical radiographs.
Histologic Features:
1.Bone cortex is thin and porous
2. Bone trabeculae are thin, delicate and widely separated
3. Many osteoblasts and osteocytes are present but formation and organization of osteoid is deficient
4. Less bone tissue than normal, most of woven bone with collagen fibres of small size and random distribution.
Investigations:
1. Prenatal USG: for early diagnosis of prenatal features
2. Chorion villous biopsy: demonstrating abnormal production of type I collagen
Treatment:
No known treatment but treatment of infections if occurs.
Prognosis:
Varies from good to poor
Some Viva questions
Q. What is osteopenia? How it occurs in case of OI?
- Mutation of gene coding for type I collagen > defect of type I collagen biosynthesis (in organic matrix) > failure of foetal collagen to be transformed into mature collagen > tendency for fracture and defective bone healing called osteopenia.
Q. Why OI shows blue sclera?
- Sclera of eye become very thin due to defective type I collagen formation. Hence the pigmented choroid shows through and produces bluish colour.
Q. Why there is hearing loss in OI?
- Due to compressions of cranial nerves or their branches
Q. What are Wormian bones?
- Wormian bones are multiple sutural bones found in the skull which fail to fuse.
Q. Name of other diseases in which blue sclera can be seen.
- 1. Osteopetrosis
2. Paget's disease
3. Foetal Rickets
4. Turner syndrome
5. Marfan syndrome
6. Ehlers-Danlos syndrome
7. Normal infants
Some MCQS
1. Brittle bone disease is
a. Osteopetrosis
b. Osteogenesis imperfecta
c. Fibrous dysplasia
d. Paget's disease
Correct answer is b
2. Osteogenesis imperfecta is due to abnormal collagen
a. Type I
b. Type II
c. Type III
d. Type IV
Correct answer is type I
3. Most severe type of osteogenesis imperfecta is
a. Type I
b. Type II
c. Type III
d. Type IV
Correct answer is b
4. Most common and mildest type of osteogenesis imperfecta is
a. Type I
b. Type II
c. Type III
d. Type IV
Correct answer is a
5. Class III malocclusions in osteogenesis imperfecta are due to
a. Maxillary hypoplasia
b. Mandibular hypoplasia
c. Both equally
d. None of the above
Correct answer is a
6. Opalescent dentin can be seen in
a. Osteopetrosis
b. Osteogenesis imperfecta
c. Fibrous dysplasia
d. Paget's disease
Correct answer is b
7. Multiple wormian bones is the feature of
a. Osteopetrosis
b. Osteogenesis imperfecta
c. Fibrous dysplasia
d. Paget's disease
Correct answer is b
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