Osteochondrodysplasia | |
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Other names | Skeletal dysplasia |
Specialty | Orthopedic |
An osteochondrodysplasia, [note 1] or skeletal dysplasia, is a disorder of the development of bone and cartilage. [1] Osteochondrodysplasias are rare diseases. About 1 in 5,000 babies are born with some type of skeletal dysplasia. [2] Nonetheless, if taken collectively, genetic skeletal dysplasias or osteochondrodysplasias comprise a recognizable group of genetically determined disorders with generalized skeletal affection. These disorders lead to disproportionate short stature and bone abnormalities, particularly in the arms, legs, and spine. [3] Skeletal dysplasia can result in marked functional limitation and even mortality.
Osteochondrodysplasias or skeletal dysplasia subtypes can overlap in clinical aspects, therefore plain radiography is absolutely necessary to establish an accurate diagnosis. [4] Magnetic resonance imaging can provide further diagnostic insights and guide treatment strategies especially in cases of spinal involvement. As some disorders that cause skeletal dysplasia have treatments available, early diagnosis is particularly important, but may be challenging due to overlapping features and symptoms [5] that may also be common in unaffected children.
Achondroplasia is a type of autosomal dominant genetic disorder that is the most common cause of dwarfism. It is also the most common type of non-lethal osteochondrodysplasia or skeletal dysplasia. The prevalence is approximately 1 in 25,000 births. [6] Achondroplastic dwarfs have short stature, with an average adult height of 131 cm (4 feet, 3 inches) for males and 123 cm (4 feet, 0 inches) for females. In achondroplasia the dwarfism is readily apparent at birth. likewise, craniofacial abnormalities in the form of macrocephaly and mid-face hypoplasia are present at birth. The previous clinical findings differentiate between achondroplasia and pseudoachondroplasia in which dwarfism is not recognizable at birth and craniofacial abnormalities are not considered a disease feature. Plain radiography plays an additional and important role in the differential diagnosis of achondroplasia. [4]
Pseudoachondroplasia is an osteochondrodysplasia made distinctive by disproportionate short stature, hip and knee deformities, brachydactyly (short fingers) and ligamentous laxity. It affects at least 1 in 20,000 individuals. Pseudoachondroplasia is inherited in an autosomal dominant manner and is caused solely by mutations in the cartilage oligomeric matrix protein COMP gene. [7] It's distinguished by a moderate to severe form of disproportionate short-limb short stature. The limb shortening is fundamentally confined to the proximal limb segments i.e., Femurs and humeri. A known presenting feature is a waddling gait, noticed at the onset of walking. A prompt diagnosis of a skeletal dysplasia in general and Pseudoachondroplasia in specific is still based upon a comprehensive clinical and radiographic correlation. [4] A detailed radiographic examination of the axial and appendicular skeleton is invaluable for the differential diagnosis of Pseudoachondroplasia. Coxa vara (reduced neck shaft angle), broad femoral necks, short femurs and humeri, and bullet-shaped vertebrae are noticeable radiographic features. Additionally, the presence of metaphyseal broadening, cupping and dense line of ossification about the knee can simulate rachitic changes. These radiographic features are collectively known as rachitic-like changes. The presence of epiphyseal changes serves as an important differentiating feature from achondroplasia. [4]
COL1A1/2-related osteogenesis imperfecta is inherited in an autosomal dominant manner. The proportion of cases caused by a De novo COL1A1 or COL1A2 mutations are the cause of osteogenesis imperfecta in the vast majority of perinatally lethal osteogenesis imperfecta, and progressively deforming osteogenesis imperfecta. In classic non-deforming osteogenesis imperfecta with blue sclerae or common variable osteogenesis imperfecta with normal sclerae, nearly 60% of cases are de novo. COL1A1/2-related osteogenesis imperfecta is identified by repeated fractures with trivial trauma, defective dentinogenesis imperfecta (DI), and hearing loss. The clinical features of COL1A1/2-related osteogenesis imperfecta can be highly variable ranging from severe and lethal perinatal fractures to individuals with minimal tendency to repeated fractures and skeletal deformities and with a normal stature and life span. In between the clinical spectrum may include individuals with various degrees of disabling skeletal deformities and short stature. [8] The radiographic findings of osteogenesis imperfecta include; long bone deformations such as bowing of the tibias and femurs, pencil-like deformity and tapering of bones, cortical thinning and rarefaction, pathologic fractures at various degrees of healing, bone shortening and vertebral wedging. [4] Accordingly, COL1A1/2-related osteogenesis imperfecta has been classified into four sub-types (I, II, III, and IV) built upon the diversity of the radioclinical features. [9]
Mucopolysaccharidoses (MPS) constitute a commonly seen group of osteochondrodysplasias. Mucopolysaccharidosis can cause a wide spectrum of clinical and radiologic manifestations ranging from mild skeletal and systemic involvement to severe life-threatening manifestations. It is caused by a contiguous gene duplication or deletion syndrome in which multiple genes are involved. All forms of MPS are inherited in an autosomal recessive pattern, except fir of MPS II; Hunter syndrome which is X-linked. [10] They are caused by an abnormal function of the lysosomal enzymes, which blocks degradation of mucopolysaccharides and leads to accumulation of harmful byproducts, namely, heparan sulfate, dermatan sulfate, and keratan sulfate. [10] The resulting cellular malfunction can lead to a diverse array of skeletal and visceral manifestations. MPS have been subcategorized according to the type of enzyme inadequacy and glycoprotein accumulated. [11]
Cleidocranial dysostosis is a general skeletal condition named for the collarbone (cleido-) and cranium deformities which people with it often have. Common features include: [12]
Fibrous dysplasia causes bone thinning [13] and growths or lesions in one or more bones of the human body.
These lesions are tumor-like growths that consist of replacement of the medullary bone with fibrous tissue, causing the expansion and weakening of the areas of bone involved. Especially when involving the skull or facial bones, the lesions can cause externally visible deformities. The skull is often, but not necessarily, affected, and any other bones can be involved. [14]
Langer–Giedion syndrome is a very rare genetic disorder caused by a deletion of chromosomal material. Diagnosis is usually made at birth or in early childhood. The features associated with this condition include mild to moderate learning difficulties, short stature, unique facial features, small head and skeletal abnormalities including bony growths projecting from the surfaces of bones. [15]
Maffucci syndrome is a sporadic disease characterized by the presence of multiple enchondromas associated with multiple simple or cavernous soft tissue hemangiomas. Also lymphangiomas may be apparent. [16]
Patients are normal at birth and the syndrome manifests during childhood and puberty. The enchondromas affect the extremities and their distribution is asymmetrical. [17]
Osteosclerosis, an elevation in bone density, [18] is normally detected on an X-ray as an area of whiteness and is where the bone density has significantly increased.
The diagnosis is mainly based upon delineating the specific clinical and radiographic pattern of skeletal involvement. However, the different types of skeletal dysplasia can overlap considerably in their clinical presentation. Molecular or genetic analysis may be required to resolve diagnostic difficulties. [4] [20]
Juvenile idiopathic arthritis may closely resemble the clinical presentation of some osteochondrodysplasias or genetic skeletal dysplsias. In that, both conditions can present with swollen, stiff and deformed joints. [20] [21]
Type II collagen disorders are caused by variants in the COL2A1 gene. Type II collagen disorders can result in mild disease or severe which can cause death within weeks of birth. Infants with the severe form of the disease would be born with clear indications of the disease, such as disproportionate short stature, skeletal dysplasia, distinctive eye abnormalities, cleft palate, and others. However, infants with mild disease may only experience arthritis at birth, but may progress to more severe disease later in life. Early diagnosis can be challenging. Furthermore, type II collagenopathies have significant phenotypic overlap with conditions such as MPS. Guidelines are available to ensure healthcare professional are aware of the conditions and the symptoms of disease to support efficient diagnosis. [22]
Emerging therapies for genetic skeletal dysplasias include enzyme replacement therapy, [23] small molecule therapy, [24] hematopoietic stem cell transplantation [25] [26] and gene therapy. These therapies aim at preventing disease progression and thus improving quality of life. Enzyme replacement therapies are some of the mucopolysaccharidoses [23] and Gaucher disease. [27] Results have shown effectivity of enzyme replacement therapy. Hematopoietic stem cell transplantation can be lifesaving for some disorders, such as with malignant infantile osteopetrosis. [25] [26]
Even with treatments such as enzyme replacement therapy and stem cell transplantation, people with skeletal dysplasia often require orthopedic surgery and other disease management interventions. There is a lack of information available to support these patients as most physicians may only see one or two skeletal dysplasia patients in their lifetime. Guidelines are available to support best practices for managing several areas of skeletal dysplasia, such as the craniofacial aspects of skeletal dysplasia, [5] spinal disorders, [5] diagnosis and management of type II collagen disorders, [22] pregnancy of people with skeletal dysplasia, [28] peri-operative management, [29] and foramen magnum stenosis in achondroplasia. [30] Written and video resources for patients with skeletal dysplasia and caregivers are also available.
Timely management of skeletal dysplasia is important to combat functional deterioration. [4] Due to rarity of the individual disorders that cause skeletal dysplasia, management can be challenging if a patient does not have access to a facility that has physicians who specialize in skeletal dysplasia. Guidelines have been developed for the management different aspects of skeletal dysplasia, [31] including best practices for managing craniofacial [5] and spinal manifestations, [5] diagnosis and management of type II collagen disorders, [22] pregnancy of people with skeletal dysplasia, [28] peri-operative management, [29] and foramen magnum stenosis in achondroplasia. [30]
Achondroplasia is a genetic disorder with an autosomal dominant pattern of inheritance whose primary feature is dwarfism. It is the most common cause of dwarfism and affects about 1 in 27,500 people. In those with the condition, the arms and legs are short, while the torso is typically of normal length. Those affected have an average adult height of 131 centimetres for males and 123 centimetres (4 ft) for females. Other features can include an enlarged head with prominent forehead and underdevelopment of the midface. Complications can include sleep apnea or recurrent ear infections. Achondroplasia includes the extremely rare short-limb skeletal dysplasia with severe combined immunodeficiency.
Dwarfism is a condition wherein an organism is exceptionally small, and mostly occurs in the animal kingdom. In humans, it is sometimes defined as an adult height of less than 147 centimetres, regardless of sex; the average adult height among people with dwarfism is 120 centimetres (4 ft). Disproportionate dwarfism is characterized by either short limbs or a short torso. In cases of proportionate dwarfism, both the limbs and torso are unusually small. Intelligence is usually normal, and most have a nearly normal life expectancy. People with dwarfism can usually bear children, though there are additional risks to the mother and child depending upon the underlying condition.
Osteopetrosis, literally 'stone bone', also known as marble bone disease or Albers-Schönberg disease, is an extremely rare inherited disorder whereby the bones harden, becoming denser, in contrast to more prevalent conditions like osteoporosis, in which the bones become less dense and more brittle, or osteomalacia, in which the bones soften. Osteopetrosis can cause bones to dissolve and break.
Osteogenesis imperfecta, colloquially known as brittle bone disease, is a group of genetic disorders that all result in bones that break easily. The range of symptoms—on the skeleton as well as on the body's other organs—may be mild to severe. Symptoms found in various types of OI include whites of the eye (sclerae) that are blue instead, short stature, loose joints, hearing loss, breathing problems and problems with the teeth. Potentially life-threatening complications, all of which become more common in more severe OI, include: tearing (dissection) of the major arteries, such as the aorta; pulmonary valve insufficiency secondary to distortion of the ribcage; and basilar invagination.
Short stature refers to a height of a human which is below typical. Whether a person is considered short depends on the context. Because of the lack of preciseness, there is often disagreement about the degree of shortness that should be called short. Dwarfism is the condition of being very short, often caused by a medical condition. In a medical context, short stature is typically defined as an adult height that is more than two standard deviations below a population’s mean for age and sex, which corresponds to the shortest 2.3% of individuals in that population.
Collagen, type I, alpha 1, also known as alpha-1 type I collagen, is a protein that in humans is encoded by the COL1A1 gene. COL1A1 encodes the major component of type I collagen, the fibrillar collagen found in most connective tissues, including cartilage.
Dentinogenesis imperfecta (DI) is a genetic disorder of tooth development. It is inherited in an autosomal dominant pattern, as a result of mutations on chromosome 4q21, in the dentine sialophosphoprotein gene (DSPP). It is one of the most frequently occurring autosomal dominant features in humans. Dentinogenesis imperfecta affects an estimated 1 in 6,000-8,000 people.
Cleidocranial dysostosis (CCD), also called cleidocranial dysplasia, is a birth defect that mostly affects the bones and teeth. The collarbones are typically either poorly developed or absent, which allows the shoulders to be brought close together. The front of the skull often does not close until later, and those affected are often shorter than average. Other symptoms may include a prominent forehead, wide set eyes, abnormal teeth, and a flat nose. Symptoms vary among people; however, intelligence is typically unaffected.
Rhizomelia refers to either a disproportion of the length of the proximal limb, such as the shortened limbs of achondroplasia, or some other disorder of the hip or shoulder.
Multiple epiphyseal dysplasia (MED), also known as Fairbank's disease, is a rare genetic disorder that affects the growing ends of bones. Long bones normally elongate by expansion of cartilage in the growth plate near their ends. As it expands outward from the growth plate, the cartilage mineralizes and hardens to become bone (ossification). In MED, this process is defective.
Dentin dysplasia (DD) is a rare genetic developmental disorder affecting dentine production of the teeth, commonly exhibiting an autosomal dominant inheritance that causes malformation of the root. It affects both primary and permanent dentitions in approximately 1 in every 100,000 patients. It is characterized by the presence of normal enamel but atypical dentin with abnormal pulpal morphology. Witkop in 1972 classified DD into two types which are Type I (DD-1) is the radicular type, and type II (DD-2) is the coronal type. DD-1 has been further divided into 4 different subtypes (DD-1a,1b,1c,1d) based on the radiographic features.
Pseudoachondroplasia is an inherited disorder of bone growth. It is a genetic autosomal dominant disorder. It is generally not discovered until 2–3 years of age, since growth is normal at first. Pseudoachondroplasia is usually first detected by a drop of linear growth in contrast to peers, a waddling gait or arising lower limb deformities.
Fibroblast growth factor receptor 3 (FGFR-3) is a protein that in humans is encoded by the FGFR3 gene. FGFR3 has also been designated as CD333. The gene, which is located on chromosome 4, location p16.3, is expressed in tissues such as the cartilage, brain, intestine, and kidneys.
Bone disease refers to the medical conditions which affect the bone.
Boomerang dysplasia is a lethal form of osteochondrodysplasia known for a characteristic congenital feature in which bones of the arms and legs are malformed into the shape of a boomerang. Death usually occurs in early infancy due to complications arising from overwhelming systemic bone malformations.
Pycnodysostosis, is a lysosomal storage disease of the bone caused by a mutation in the gene that codes the enzyme cathepsin K. It is also known as PKND and PYCD.
Eiken syndrome, also known as "Eiken skeletal dysplasia", is a rare autosomal bone dysplasia with a skeletal phenotype which has been described in a unique consanguineous family, where it segregates as a recessive trait. First described in 1985, the syndrome primarily affects the development of bones, leading to short stature, long limbs, and joint dislocations. Eiken syndrome is caused by mutations in the PTH1R gene, located on chromosome 3, and is involved in skeletal development.
Bruck syndrome is characterized as the combination of arthrogryposis multiplex congenita and osteogenesis imperfecta. Both diseases are uncommon, but concurrence is extremely rare which makes Bruck syndrome very difficult to research. Bruck syndrome is thought to be an atypical variant of osteogenesis imperfecta most resembling type III, if not its own disease. Multiple gene mutations associated with osteogenesis imperfecta are not seen in Bruck syndrome. Many affected individuals are within the same family, and pedigree data supports that the disease is acquired through autosomal recessive inheritance. Bruck syndrome has features of congenital contractures, bone fragility, recurring bone fractures, flexion joint and limb deformities, pterygia, short body height, and progressive kyphoscoliosis. Individuals encounter restricted mobility and pulmonary function. A reduction in bone mineral content and larger hydroxyapatite crystals are also detectable Joint contractures are primarily bilateral and symmetrical, and most prone to ankles. Bruck syndrome has no effect on intelligence, vision, or hearing.
Langer Mesomelic Dysplasia (LMD) is a rare congenital disorder characterised by altered bone formation, which typically causes affected individuals to experience shortening of the bones of the extremities as well as an abnormally short stature.
Wormian bone-multiple fractures-dentinogenesis imperfecta-skeletal dysplasia syndrome is a rare genetic bone disorder which is characterized by the presence of wormian bones in the skull, dentinogenesis imperfecta, recurrent bone fractures, hypertelorism, and eye puffiness. This disorder is unique from osteogenesis imperfecta because of the presence of cortical defects and the absence of defective collagen or osteopenia. It is not exactly known whether this condition is autosomal dominant or autosomal recessive.