【Overview】.
Chondrodysplasia is also known as fetal-type chondrotrophic disorder, chondrotrophic dwarf, etc. It is a congenital developmental abnormality due to defective endochondral ossification, mainly affecting long bones, and clinically manifests as a special type of dwarf-short-limbed dwarf. Intellectual and physical development is good, and patients often act as acrobatic clowns in theatrical troupes or circuses.
【Treatment measures
Generally not difficult, in typical cases, it needs to be distinguished from dwarf caused by other causes.
①Chondrodysplasia hypoplasia: dwarfism is less obvious and the head is normal.
②Chondro-epiphyseal hypoplasia, i.e. Ellis Van-Creveld syndrome, is a short-limbed type of dwarf with thoracic deformity and cardiac lesions.
(3) Epiphyseal hypoplasia is also short-limbed dwarf, often with destruction of proximal large joints, normal skull, flattened vertebral bodies, and vertebral ossification centers coinciding with each other. The thoracic hypoplasia is bell-shaped.
④Rickets and Cretinism. Rickets has typical clinical and X-ray manifestations, easy to distinguish; and Cretinism is often accompanied by mental retardation.
Etiology
It is a congenital developmental abnormality, and has a clear hereditary and family history of autosomal dominant inheritance. If one parent has the disease, 1/2 of the children can get the disease; if both parents are affected, almost all children will be affected. Since many patients do not marry or have difficult childbirth, resulting in no next generation, thus affecting the form of inheritance. So sporadic cases account for 90% of cases. Of course, there are also people who have the disease due to genetic mutations. In twin births, one can be affected or both can be affected, slightly more in women than in men.
Pathological changes
The basic pathological changes occur in the process of cartilage osteogenesis, the longitudinal growth of long bones is blocked, while the process of intra-membranous osteogenesis is not affected, so the thickness of the bone is normal, but the length is relatively thicker due to the shortening. Chondrocytes in the epiphysis can occur and proliferate, but cannot undergo normal calcification and ossification, resulting in enlarged bone ends. Microscopically, chondrocytes cannot be arranged in a regular columnar pattern as normal, but are scattered and irregularly stacked. The hierarchy of several areas of the ossification process, such as the resting zone, proliferation zone, hypertrophy and preparatory calcification zone, is also disturbed, capillaries in the epiphysis cannot enter the epiphysis regularly for normal resorption, and mature chondrocytes cannot calcify, affecting bone growth. Extensive mucinous degeneration of the cartilage with swollen cells, enlarged nuclei, and a semi-fluid structure of the matrix can also be seen. Cartilage ossification at the lesion site is delayed and patchily distributed, while the calcification process between the patches is relatively normal.
【Clinical manifestations】.
(A) Pygmy
This disease is the most common cause of dwarfism. The fetus is delivered with a normal length body and shorter limbs, and this difference becomes obvious later on, with the proximal limbs such as the humerus and femur being shorter than the distal bones, and the affected child being fat and bloated. By maturity, the average height was 131±5.6 cm in males and 124±5.9 cm in females. 97 cm and 104 cm have been reported in the literature. The midpoint of the child’s body is above the umbilicus and sometimes even at the lower end of the sternum. Because of the short limbs, the face can touch the toes when the lower limbs are in the extended position.
(ii) Enlarged skull Some patients have mild hydrocephalus, protrusion of the dome and forehead, and saddle-shaped nasal wonk.
(iii) posterior protrusion of the thoracic vertebrae and anterior protrusion of the lumbar vertebrae, the latter being obvious. The sacrum is more horizontal making the characteristic protrusion of the hip.
(iv) The thoracic cavity is flat and small, and the rib cage is abnormally short.
(v) The fingers are thick and short, separated, often seen as a group of 4 or 5 fingers, 2 or 3 fingers as a group, and the thumb as a group, resembling a “trident” (Figure 1). In some patients, the elbow extension is mildly restricted.
(F) The lower extremities are bowed, and there is a rolling gait (rolling).
(vii) Normal intellectual development, good teeth, strong muscle strength, and normal sexual function.
X ray performance
The skull cap is large, the forehead is prominent, the parietal bone and occipital bone are also more protruding, but the skull base is short, the occipital foramen is small and funnel-shaped, its diameter may only be 1/2 of normal.
The long bones are shortened, the diaphysis is thickened, the medullary cavity is small, and the epiphysis may be fragmented or uneven. In the knee joint, it is common to see a “V” shaped separation of the bone ends, and the epiphyseal ossification center is embedded in this V-shaped notch. Because the ossification center is close to the diaphysis, the joint space has a widened appearance. The lower extremity is bowed, the fibula is longer than the tibia, and the ulna is longer than the radius in the upper extremity.
(iii) The thickness of the vertebrae is reduced, but the reduction in the full length of the spine is relatively much less than the reduction in the length of the extremities. From the first lumbar vertebra to the fifth lumbar vertebra, the intervertebral arch distance becomes progressively smaller. Myelogram shows narrowing of the spinal canal with multiple posterior disc protrusions.
The pelvis was narrow, the skeleton was flat and round, the diameter of each was small, the acetabulum was posteriorly displaced and close to the sciatic notch, there was hip inversion, and the size of the acetabulum and femoral head was asymmetrical. The ribs are short, and the sternum is wide and thick. The scapular angle is not sharp, and the scapular glenoid is shallow and small.
Prognosis
If the infant does not die prematurely, he or she can perform various jobs in adulthood and has a good prognosis. In a small number of patients, hydrocephalus occurs due to small occipital foramen. The incidence of spinal stenosis can be up to 40%, mostly in the lumbar spine. Occasionally, it is found in the cervical or thoracic spine, resulting in compression of the nerve roots or spinal cord, requiring laminectomy for decompression or intervertebral foramen enlargement. Occasionally, osteotomies are performed due to deformities of the lower extremities. There is no specific treatment for the cause of the disease.