Introduction:
About 206 bones constitute the human body to protect the internal organs, provide structural support, and bodily aid movements. It undergoes remodeling, where the old bone is replaced with new. It comprises the outer cortical (80 %) and inner trabecular or spongy parts (20 %) that constitute essential components like collagen (protein) and calcium phosphate. These critical components significantly maintain the strength and flexibility of bone. This article illustrates a bone disorder caused due to improper collagen formation.
What Is a Brittle Bone Disease?
Brittle bone disease, also known as osteogenesis imperfecta (OI), is a rare genetic disorder affecting the connective tissue of the body and leading to improper bone formation. Therefore, the bones become extremely weak and tend to break easily. About one in 10,000 to 20,000 individuals are affected worldwide.
It is also known by the following names:
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Fragilitas ossium.
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Vrolik disease.
What Causes Brittle Bone Disease?
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The leading cause of osteogenesis imperfecta is genetic changes (mutations). COL1A1 and COL2A2 are the genes that instruct the production of type I collagen. Type I collagen is majorly present in the bones, ligaments, skin, and other body connective tissues. Any alterations in the COL1A1 gene result in decreased production of type I collagen, thus causing osteogenesis imperfecta type 1.
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The mutation in either COL1A1 or COL2A2 may produce defective collagen that leads to severe forms of the diseases (type II, III, and IV). Several other gene mutations are responsible for causing the other rare conditions of osteogenesis imperfecta.
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There is a 50 % chance for the child to acquire the defective gene from their parents. About 25 % of children obtain the inactive (recessive) form and remain carriers of the disease.
What Are the Signs and Symptoms of Brittle Bone Disease?
The manifestations of the ailment differ from individual to individual. Even individuals within the same family, or those with identical forms of osteogenesis imperfecta, can exhibit varying symptoms. Osteogenesis imperfecta typically presents with various types, each with distinct symptoms.
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Type 1: This represents the mildest and most prevalent form of brittle bone disease. While collagen levels are normal, they are insufficient. Individuals with type 1 experience bones prone to easier fractures, yet typically maintain normal bone structure. Initial fractures commonly occur during early childhood when walking begins, with decreased fracture frequency post-puberty. Notably, a bluish tint may appear in the sclera(whites of the eyes), and adult-onset hearing loss may also occur.
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Type 2: This represents the most severe form. Collagen formation is abnormal. Infants with type 2 typically present with numerous fractures at birth, exhibit small stature, and experience significant respiratory challenges, often leading to low survival rates.
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Type 3: Collagen formation is abnormal, leading to frequent bone fractures at birth. As children age, they tend to experience increased susceptibility to bone breakage and typically have shorter stature compared to peers. Additional symptoms may include bone deformities such as outward pointing ribcage, bowed legs, triangular facial structure, and curved spine, potentially life-threatening breathing difficulties, fragile teeth, adult-onset hearing loss, and other complications. Notably, a bluish tint may be evident in the sclera.
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Type 4: In type 4, collagen formation is also abnormal. Children commonly experience frequent bone fractures, which may diminish in frequency after puberty. Additionally, they exhibit bone deformities akin to those seen in type 3. Shorter stature compared to peers and adult onset hearing loss are typical features of this type.
How to Diagnose a Brittle Bone Disease?
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Physical Examination - The doctor enquires about the family history and looks for the classical signs of brittle bone disease.
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Radiographic Examination - The doctor also orders a plain radiograph to view the fractures, callus formation, and other long bone and rib cage deformities.
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Ultrasound (USG) Examination - The prenatal ultrasound examination aids in visualizing the severe forms of OI that exhibit limb length discrepancy, fractures, etc.
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Amniocentesis - A sample of amniotic fluid surrounding the fetus inside the uterus is collected to determine any genetic changes.
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Bone Density Test - The bones that lack appropriate minerals tend to be fragile and break easily. Devices are used to measure bone density to determine the risk of fracture.
What Are the Similar Conditions?
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Achondroplasia - A genetic disorder characterized by the lack of cartilage formation. Therefore, abnormal bone formation occurs, causing short stature, large head, abnormal facial features, etc.
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Osteopetrosis - An abnormal growth of bone happens, leading to frequent fractures. Other visual, hearing, and dental abnormalities also appear in individuals with osteopetrosis.
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Hypophosphatasia - An inherited disorder that disturbs the bone’s mineralization. It weakens the bone, and in infants, abnormally shaped chests and short limbs are characteristic features.
How to Treat a Brittle Bone Disease?
The osteogenesis imperfecta does not entirely resolve. However, specific supportive care may improve the quality of life. It includes:
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Medications - Intravenous administration of Bisphosphonate slows down bone loss, thereby maintaining the bone mass and improving its strength. Other drugs like Teriparatide also improve bone strength. The doctor may suggest analgesics to relieve the pain.
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Physical Therapy - A therapist helps children and adults to learn activities that will enhance movements and muscle strength. It will also help to avoid further injuries and recover from old fractures.
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Assistive Devices - Wheelchairs, walkers, and crutches (long sticks held underarms for support) assist in performing day-to-day activities.
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Hearing Aids - Hearing is significantly impaired in children with brittle bone disease. The audiologist may order electronic devices that improve hearing (worn outside the ear). Cochlear implants (surgically placed devices) also improve hearing in severe deafness.
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Oral Care - The tooth structure is significantly affected, and a regular visit with the dentist is essential to enhance its appearance and alignment.
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Surgery - Certain procedures assist in stabilizing and healing fractured bones. The surgeon places metal rods in long, severely deformed bones during the process.
Conclusion:
Osteogenesis imperfecta is a chronic condition, and the care given to children and adults is essential in improving their standard of living. Support from the therapist, pediatrician, orthopedics, and dentist is critical in enhancing joint movements and relieving pain. In addition, following regular exercise and intake of nutritious foods may improve the individual's overall well-being.
