Introduction
Meow syndrome(cats cry syndrome) is a chromosomal deletion syndrome caused by short arm loss (5p deletion) of chromosome 5, also known as short-arm abscess syndrome of chromosome 5, which is one of the most typical chromosomal deletion syndromes. The main clinical manifestations are the cat crying at birth, the typical deformity of the head and face, the small head round face, wide eye distance, small mandible, strabismus, wide flat nose and low ear, etc., with poor growth and severe mental retardation.
Cause
(1) Causes of the disease
The meow syndrome is caused by a short-armed deletion of chromosome 5 of group B, which is early replication, and most of the deletions are the result of two breaks. If the break occurs on the short arm and the long arm, respectively, a loop will be formed. Chromosomes, there is a translocation of chromosome 5 to the chromosomes of group C, D or G, chimerism and inversion between arms.
In theory, there are at least four reasons for the deletion of the chromosomal part: terminal deletion, intermediate deletion, translocation and unequal exchange in the short arm. It has been found that the missing part has 5p14, so 5p14 is considered to be the characteristic of meow syndrome. Area. It has been reported that the short length of the short arm is 30% of the short arm, 85% of the elderly, usually 50%, and 10% of the reported loss can also cause mild symptoms. From the perspective of changes in chromosomes, there is a grammatical gene on the short arm of chromosome 5, and when it is missing here, a variation of the pronunciation tone can occur.
(two) pathogenesis
Cytogenetic studies have confirmed that most short-armed deletions of chromosome 5 are caused by two breaks of chromosomes during mitosis. If the break occurs in the short arm, it is an intermediate deletion, if the break occurs in the short arm and the long arm, respectively. On top, a circular chromosome is formed. In some cases, the chromosome 5 of the patient is translocated to the chromosome of group C, D or G to form a chimera or an inversion between arms.
The degree of clinical manifestation was related to the location of the 5p deletion, but there was no significant correlation with the length of the deletion. Therefore, it was proposed to determine the key areas based on the clinical manifestations of the child (cat crying and typical facial features). Accordingly, the key region of meow syndrome is located at 5p15.2, located between the two genetic markers D5S713 and D5S18, which account for about 10% of the total length of 5p, containing 400-600 kb DNA. The disease provides genetic information.
symptom
The sick child was born with low body weight, the average body weight was less than 2500g, and the body length was lower than that of normal children, with an average head circumference of 31cm. Growth disorders, the most prominent feature is the weak, sad, and Mimi-like crying in infancy. This kind of crying occurs when exhaling, does not appear when inhaling, and its mechanism is unknown. Some people think that It may be that the cartilage is weak or the softening of the throat causes the air leaking from the throat during exhalation, and some people think it is related to brain damage. Typical crying often disappears early in childhood, but some older children and adults still have unique cries.
The child's craniofacial dysplasia, the head is small and round, full moon face. The distance between the eyes is too wide and the small mandible is obvious. The cleft palate is slightly obliquely outward and downward, with internal ecdysis, strabismus, and cataract. The bridge of the nose is wide and flat. Small ear, slightly lower, sometimes narrow ear canal. With the change of age, the small head persists, but the face becomes longer and the mandibular dysplasia is more obvious. Dental caries, high arches. One third of the cases may have congenital cardiovascular malformations. Kidney and various skeletal deformities (such as scoliosis, and finger, toe and rib deformities) are also visible. The muscle tension of the limbs is low, the muscle tension increases with age, and the reflex increases. The development is obviously backward. When I am 2 years old, I will sit. When I am 4 years old, I will walk away. There is a kind of defensive gait. Some sick children are bedridden like baby, can't talk or can only say a few words, the intelligence is low, and the IQ is less than 20.
diagnosis
In addition to the clinical phenotype, the diagnosis of meow syndrome is also the main basis for cytogenetic testing. Ordinary karyotype analysis can make a preliminary diagnosis, but because it is difficult to accurately locate, it is often difficult to make a definitive diagnosis of chromosomal translocation loss or other special types of deletion. In this case, FISH technology should be used for further precise positioning to clear the deficiency. The starting point.
Identification
Different from other chromosomal aberrations, such as 21-trisomy, 13-trisomy, 8-trisomy, and 9-trisomy syndrome, cell chromosome examination can help identify.
complication
Growth disorders, strabismus, cataract, 1/3 cases may have congenital cardiovascular malformations, kidney and various skeletal deformities, spastic gait.
treatment
Western medicine treatment
There is currently no ideal treatment, mainly symptomatic supportive treatment and good care.
The above content is for reference only, please consult the relevant physician or relevant medical institution if necessary.
prevention
Since 12% of meow syndrome is derived from a chromosomal balance translocation of one of the parents, it is important to have a chromosomal examination of the parent's parents to predict the likelihood of recurrence, reducing or eliminating the birth of the child.
Prognosis
The mortality rate is low, and most of the sick children can live to adults, but their weight and height are lower than normal.
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