Introduction
Cartilage hypoplasia(achondroplasia) is also known as chondrodystrophia fetalis, chondrodystrophic dwarfism and the like. It is a congenital dysplasia due to defects in endochondral ossification, which mainly affects long bones. The clinical manifestation is a special type of dwarf-short limb dwarf. The intelligence and physical strength are well developed, and the patient often acts as an acrobatic clown for the troupe or circus. Warkany has estimated that there are about 65,000 patients with dysplasia in the world, indicating that this deformity is more common.
Cause
(1) Causes of the disease
The achondroplasia is an autosomal dominant hereditary disease. A large proportion of cases are stillbirth or death in the neonatal period. Most of the parents have normal development, suggesting that it may be the result of spontaneous gene mutation. Molecular genetic studies have found that the gene encoding the fibroblast growth factor receptor has a point mutation on the short arm of the fourth pair of chromosomes.
The second generation of the disease was seen in the youngest boy, and the parents were normal. This is due to a new mutation in the gene. By the third generation, both couples had cartilage insufficiency, so there were 2 children with cartilage insufficiency, 1 stillbirth, and 1 normal.
(two) pathogenesis
At the metaphysis of all bones, especially at the metaphyseal end of the long tubular bone, the cartilage exhibits obvious mucoid degeneration. Intrachondral ossification, but the internalization of the membrane is not affected, the chondrocytes lose the function of normal alignment and growth, resulting in a slow growth of the long bone, and the diameter of the backbone is not affected due to the normalization of the membrane internalization. There are similar developmental disorders in the cartilage junction of the sphenoid and occipital bones at the base of the skull. Since the callus itself is not stunted, there is no degenerative change in the joint at an early stage.
symptom
The main clinical manifestations of the disease:
At birth, the trunk of the child is found to be out of proportion to the limbs. The head is large and the limbs are short and the trunk length is normal. The proximal part of the limb is more affected than the distal end. For example, the femur is more sacral and the humerus. The humerus is shorter than the ulna and the tibia. This feature is more obvious with age and gradually forms a dwarf deformity. The facial features are nasal bridge collapse, mandibular protrusion and forehead width. The middle finger and the ring finger cannot be close together, called the trident hand. There may be flexion contracture of the elbow joint and dislocation of the humeral head. The lower limbs are short and curved and arched, and the muscles are particularly bloated. The length of the spine is normal, but there is a thoracic kyphosis in infancy. Infancy occipital stenosis is also common in children, the main symptoms are low back pain and intermittent claudication. The patient's intelligence is generally unaffected.
diagnosis
According to the patient's typical body and appearance, the limbs are reduced, and the fingers are trident-shaped, it is not difficult to make a diagnosis.
Identification
The diagnosis of this disease is generally not difficult, and atypical cases need to be distinguished from gnomes caused by other causes.
1 Hypochondroplasia pygmy performance is not obvious, the head is normal.
2 chondro-ectodermal dysplasia, namely Ellis Van-Creveld syndrome, is a short-limb dwarf with chest deformity and heart disease, and finger and nail dysplasia. The shortened part of the limb often occurs in the distal segment of the bone.
3 spine-epiphyseal dysplasia. It is also a short-limb dwarf, often with the destruction of proximal large joints, normal skull, flattened vertebrae, and vertebral ossification centers. Thoracic dysplasia such as bell shape.
4 rickets and cretinism. Rickets have typical clinical and X-ray findings that are easily differentiated; cretinism is often associated with mental dysplasia.
5 The bone defects of vitamin D deficiency are characterized by blurred contours and ossification.
complication
Regarding the complications of this disease, a small number of patients develop hydrocephalus due to the smaller occipital pores. The incidence of spinal stenosis can reach 40%, mostly in the lumbar spine. Occasionally in the cervical or thoracic vertebrae, causing compression on the nerve root or spinal cord, decompression of laminectomy, or intervertebral foramen enlargement. Occasionally due to lower limb deformity for osteotomy. Can also be complicated by humeral head dislocation, elbow contracture and thoracic kyphosis.
treatment
At present, there is no way to normalize the bone development of sick children, and growth hormone is effective in some cases. A few medical centers are evaluating the effects of human growth hormone on these children. Up to now, the growth of some sick children has achieved a moderate level of improvement. However, it is not known whether these treatments can significantly increase the final height of their adulthood. Leg growth surgery can increase the height of some patients. However, such procedures require a longer treatment time and may have many complications. This type of surgery is usually performed only in some experienced centers.
The doctor will make a comprehensive evaluation of the skeletal abnormalities in children with achondroplasia, and use a special head and body growth and development table to track the growth of the child. If the head begins to become too large, the doctor should check if the child has hydrocephalus. If necessary, the neurosurgeon will implant the shunt into the shunt to divert excess brain fluid to relieve stress on the brain. The patient's bone abnormalities should also be monitored because the pressure on the spinal cord caused by it may cause difficulty breathing, leg pain and paralysis. After the child begins to walk, if the hunchback has not subsided, it may be corrected by surgery. Bent legs, especially those that become more severe or have caused pain, can also be corrected surgically.
Children with achondroplasia usually need to place a middle ear aqueduct, which helps prevent hearing loss due to frequent ear infections. Dental problems caused by crowded teeth may require extra care, an orthosis and the removal of one or more teeth. Children often start to be overweight in early childhood. Because overweight may further aggravate bone problems, nutrition guidance should be obtained to prevent obesity.
Easy to cause lumbar pain due to lumbar spinal stenosis or intervertebral disc herniation, and even lower extremity paralysis, need to do laminectomy and decompression or lumbar discectomy.
For patients with occipital foramen stenosis and brainstem and spinal cord compression, posterior occipital foramen should be decompressed to prevent sudden death. If Chiari malformation or hydrocephalus is present, it should be treated according to the condition, such as decompression or shunt surgery.
Thoracolumbosacral orthosis (TLSO) has a certain effect on the prevention and treatment of thoracic and lumbar kyphosis. Some scholars advocate that TLSO should be worn until the age of 2 when the child can sit, if the brace treatment is invalid, The kyphosis is worse or the kyphosis exceeds 40° at 5 years of age. Spinal fusion should be performed.
When the tibia is overgrown with respect to the tibia, it can cause angular deformity of the lower extremities and knee varus. It is feasible for the symptoms of the sacral osteotomy. It has also been reported that the humeral epiphysis fusion is used to correct the deformity of the lower limbs, but the effect is not certain.
The above content is for reference only, please consult the relevant physician or relevant medical institution if necessary.
prevention
There are currently no effective preventive measures for this disease, as most cases are caused by genetic mutations that are completely unpredictable by unaffected parents. Genetic counseling can help adults with selective births. In addition, early diagnosis and early treatment is the key to the prevention and treatment of this disease. If the baby does not die, he can be qualified for various jobs in adulthood with a good prognosis.
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