Patient's question:
What is Down syndrome? Does having three pairs of chromosome 21 refer to fetal malformation?Doctor's answer:
Hello, British doctor Lagdo Dow first described the clinical manifestations of Down syndrome, hence naming this disease Dow syndrome, which is also known as Down syndrome. In China, the term Down syndrome is more commonly used. In 1959, French cytogeneticist Lcjeue confirmed that the cause of this disease is an extra small G-group chromosome (later identified as chromosome 21). Therefore, this disease is also called trisomy 21 syndrome. The signs of this disease are very diverse, with abnormalities in many organs and tissues. However, the developmental deformities are usually not severe enough to be life-threatening. Newborns generally have lower average weight and length, and hypotonia. The most prominent feature is the craniofacial deformities. The head is small and round, the occiput is flat, the face is round, the nose is flat, the eyelid fissures are narrow and slanted outward upward, the interpupillary distance is too wide, the epicanthal folds are prominent, the eyelashes are short and sparse, and strabismus is common. The iris sometimes has white spots, and cataracts are often present. The mouth is small with thick lips, the tongue is large and often protrudes, the ears are small, low-set ears, and the auricles are deformed. The hair is straight and not curly. The neck and back are short and wide, with excess skin. Due to poor cartilage development, the limbs of patients are shorter. The hands are wide and fat, with transverse palmar creases, short fingers, and the fifth finger is often inwardly curved, short, or missing the middle phalanx. The abdomen is swollen due to hypotonia, so it is common to have rectus muscle separation or umbilical hernia. More than half of the patients have congenital heart disease, mainly ventricular septal defect, atrioventricular canal communication, atrial septal defect, and patent ductus arteriosus. Abdominal deformities such as duodenal stenosis, megacolon, rectal prolapse, and anal atresia are occasionally seen. Children with this syndrome have slow intellectual development, they can sit up only after one year of age, and start walking around three years old. Their personality is gentle and slow, with little aggression, and they are not very good at counting, but sometimes they have a certain memory and are good at imitating others. Intellectual disability is the most prominent and serious manifestation of this syndrome. The IQ is usually between 25 and 50. Children with better intelligence can learn to read or do simple manual labor, while those with poorer intelligence have difficulties in language and self-care. As they grow older, their IQ may continue to decline. This does not mean that the children are getting dumber, but rather that the intellectual gap compared to their peers becomes larger. In fact, through training, they can learn to do more labor and to some extent can mask the degree of intellectual disability. External genital development is usually not significantly abnormal, but males may have cryptorchidism. Spermatogenesis occurs in the testes, but sperm count is often reduced, sexual desire declines, and no fertile individuals have been reported yet. Female patients usually do not menstruate, but a few can become pregnant and give birth. There are reports of 25 female patients who have given birth to 27 children. Theoretically, about half of their children should be affected, but in reality, the ratio of affected to unaffected children is 10:17. The average life expectancy of patients is only 16.2 years. 50% of the children die before the age of 5. The mortality rate in other age groups is 5 to 6 times higher than that of the general population. Only 8% of patients live past 40, and 2.6% live past 50. The life expectancy of patients usually depends on whether they have severe congenital heart disease and digestive tract deformities, as well as the degree of reduced resistance to infection, because these are the main causes of death. In addition, the incidence of leukemia in patients is 15 times higher than that of the general population, which is also one of the causes of death. If patients survive for a longer period, facial deformities and a flat nose bridge, epicanthal folds, etc., will gradually become less apparent. However, the face becomes more withered, and the cheeks become flushed. Many patients develop cataracts and mental abnormalities before adulthood.