Achondroplasia

Introduction to achondroplasia Achilles dysplasia (achondroplasia) is also known as fetal cartilage dystrophy (chondrodystrophiafetalis), cartilage dystrophic gnome (chondrodystrophicdwarfism). 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. Intelligence and physical strength are well developed. Patients often act as acrobatic clowns in 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. basic knowledge The proportion of illness: 0.002% Susceptible people: no special people Mode of infection: non-infectious Complications: hydrocephalus

Cause of achondroplasia

(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 research found that The gene encoding the fibroblast growth factor receptor is point-mutated and located on the short arm of the fourth pair of chromosomes.

(two) pathogenesis

At the metaphysis of all bones, especially at the metaphysis of the long tubular bone, the cartilage showed obvious mucoid degeneration, endochondral ossification, but the membrane internalization was unaffected, and the chondrocytes lost their normal alignment and growth. Function, resulting in slow growth of long bones, and due to the normalization of the internalization of the membrane, the diameter of the backbone is not affected, and there is a similar developmental disorder in the cartilage of the sphenoid bone and occipital bone at the base of the skull, because the epiphysis itself is not stunted. In the early stage, there will be no degenerative changes in the joints.

Prevention of achondroplasia

There are currently no effective preventive measures for this disease, because most cases are caused by genetic mutations that are completely unpredictable by unaffected parents. Genetic counseling can help adults with selective fertility and early diagnosis. 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 tasks in adulthood, and the prognosis is good.

Complications of achondroplasia Complications hydrocephalus

Regarding the complications of this disease, a small number of patients have hydrocephalus due to small occipital pores, and the incidence of spinal stenosis can reach 40%, mostly in the lumbar vertebrae, occasionally in the cervical or thoracic vertebrae, causing nerve roots or spinal cord. Compression, the need for laminectomy decompression, or intervertebral foramen enlargement, occasionally due to lower extremity deformity for osteotomy, but also with humeral head dislocation, elbow contracture and thoracic kyphosis.

Symptoms of achondroplasia Common symptoms Limb shortening deformity Elbow deformity Neck is afraid of flexion, fearing that the neck can be flexed forward, fearing the extension of the mandibular protrusion

At birth, the trunk of the child is found to be disproportionate to the limbs. The head is large and the limbs are short, the length of the trunk is normal, and the proximal end of the limb is more affected than the distal end. For example, the femur is more squat, the tibia and the tibia are more than the ruler, and the tibia is shorter. 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, middle finger and ring finger can not be close together, called trident hand (Fig. 2), can have elbow joint Flexion contracture and dislocation of the humeral head, the lower limbs are short and curved and bowed, the muscles are particularly bloated, the spine length is normal, but there may be thoracic kyphosis during infancy, and the occipital stenosis in infants is also common in children. Symptoms are low back pain and intermittent claudication, and the patient's intelligence is generally unaffected.

According to the patient's typical body, appearance, limbs, and fingers in a trident shape, it is not difficult to make a diagnosis.

Examination of achondroplasia

1. Imaging examination

(1) X-ray inspection has the following main performances:

1 The cranial cap is large, the forehead is prominent, the parietal bone and occipital bone are also more bulging, but the skull base is short, the occipital large hole becomes smaller and funnel-shaped, and its diameter may be only 1/2 of the normal person, such as the cerebral ventricle with hydrocephalus expansion.

2 The long bones become shorter, the backbone is thicker, the medullary cavity becomes smaller, and the callus can be fragmented or irregular. In the knee joint, the common bone ends are separated by a V shape, and the ossification center of the epiphysis is embedded in the V-shaped notch. Among them, because the ossification center is close to the backbone, the joint space has a feeling of widening, the lower limbs are arched, the tibia is longer than the tibia, and the upper ulna is longer than the tibia.

3 The thickness of the vertebral body is reduced, but the reduction of the total length of the spine is relatively less than the decrease of the length of the limbs. From the first lumbar vertebrae to the fifth lumbar vertebrae, the distance between the vertebral arches gradually becomes smaller. The myelography shows that the spinal canal is narrow and there are multiple intervertebral discs. After the sudden.

4 pelvic stenosis, iliac bone flat and round, all small diameter, acetabular posterior movement, close to the sciatic notch, hip varus, asymmetrical acetabular and femoral head size, short ribs, wide and thick sternum, shoulder angle Not sharp, the shoulders are shallow and small.

(2) Magnetic resonance examination: It has a clear value for judging the degree of spinal cord compression.

2. Ultrasound examination

Prenatal monitoring of femoral development has a certain significance.

Diagnosis and diagnosis of achondroplasia

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, which is Ellis Van-Creveld syndrome, is a short-limb dwarf with chest deformity and heart disease, and refers to the development of nail teeth and the shortening of limbs. In the far segment of the bones.

3 spine-epiphyseal dysplasia, also a short-limb dwarf, often with the destruction of the proximal large joints Bell shape.

4 rickets and cretinism, rickets have typical clinical and X-ray findings, easy to distinguish; and cretinism often accompanied by mental dysplasia.

5 The bone defects of vitamin D deficiency are characterized by blurred contours and ossification.

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