Analysis of genetic characteristics of 436 children with dysplasia and detailed analysis of rare karyotype

1 Introduction

Dysplasia in children is increasingly becoming a prominent public health and social problem. Dysplasia in children affects children’s health and quality of life and the healthy and sustainable development of society. So, reducing congenital disabilities has great social significance. Therefore, it is necessary to delve into the causes of dysplasia in children.

Congenital heart disease (CHD) is one of the most common dysplasias in children. The incidence of CHD in neonates is 8–9/1,000, and nearly 1.35 million CHD neonates are born every year in the world [1]. Chromosomal causes of CHD include chromosome aneuploidies, such as Trisomy 21 (Tri21). Chromosomal aneuploidies represent 12.5% of CHD causes [2]. In addition, Tri21 syndrome, a common chromosomal disorder, is the most common cause of severe mental retardation, special facial features, and abnormal bone development in children.

Disorder of sexual development (DSD) and short stature are also the most common dysplasia symptoms in children. Sex chromosome abnormality is one of the most common causes of DSD and short stature. Common sex chromosomal disorders include Klinefelter syndrome (1/1,000–1/2,000 in male newborns), Turner syndrome (TS, approximately 1/5,000 in newborn girls), XYY syndrome (1/900 in males), and XXX syndrome (1/1,000 in newborn girls). Patients with sex chromosome diseases are often accompanied by gonadal dysplasia, secondary sexual signs dysplasia, fertility disorders, mild mental abnormalities, mental deficiencies, and other symptoms. In addition, children with TS often have short stature. Children with severe short stature are vulnerable to diverse developmental, social, and educational problems [3]. Therefore, the abnormality of the sex chromosome is one of the important causes of dysplasia in children.

There is a significant evidence in the literature that the chromosome partial monomer or trisomy can lead to severe dysplasia in children. The clinical examination of the patients with structurally abnormal chromosome 15 revealed a series of clinical symptoms, such as intellectual disability, CHD, severe growth retardation, hypertelorism, microcephalus, dysmorphology, and multiple sclerosis hyperpigmented or café-au-lait spots, short stature, and clinodactyly [4,5,6,7]. The common clinical features of the patients with partial trisomy of chromosome 8 included developmental delay, intellectual disability, mental retardation, severe hypotonia, hypospadias, skeletal anomalies, renal dysplasia, attention-deficit hyperactivity disorder, atypical facial appearance, and congenital hypoplasia of the tongue [8,9,10,11,12,13]. The short arm monosomy of chromosome 9 may present developmental delay, hypotonia, trigonocephaly, psychomotor developmental delay, learning difficulties, trigonocephaly, facial dysmorphia, and genital abnormalities [14,15].

Thus, the chromosomal abnormality is one of the important causes of dysplasia in children, which seriously endangers children’s physical and mental health and brings heavy spiritual and economic burdens to families and society. However, due to regional and ethnic differences, the reported rates of chromosomal abnormalities in patients with dysplasia vary greatly. So, we retrospectively analyzed the karyotype results of 436 children with dysplasia and conducted a detailed analysis of rare cases to clarify the chromosomal abnormality rate and distribution of abnormal chromosomes in local children with dysplasia and provide a theoretical basis for clinical diagnosis and prenatal diagnosis, and assess the risk of recurrence.

2 Patients and methods

3 Results

Chromosomal abnormalities were detected in 181 of 436 cases. The abnormal rate was 41.51%. Among them were 153 cases of autosomal abnormality (84.53%, 153/181, Table 1) and 28 cases of a sex chromosome abnormality (15.47%, 28/181, Table 2). The main clinical symptoms of 181 children with chromosomal abnormalities were intellectual disability (80.66%, 146/181), dysmorphology (71.82%, 130/181), congenital malformations (22.10%, 40/181), DSD (12.15%, 22/181), and short stature (8.29%, 15/181).

One hundred and thirty-six cases of Tri21 were detected (31.19%, 136/436), including 89 male and 47 female, with a ratio of 1.89:1. Among them, 130 cases were standard Tri21 (95.59%, 130/136), 5 cases were Robertsonian Tri21 (3.79%, 5/132) and 1 case was a chimeric type (0.74%, 1/136).

Twenty-eight cases of sex chromosome abnormalities were detected, among which 20 cases were TS (7 cases were 45,X, 13 cases were 45,X mosaic), 5 cases were 46,X,i(X)(q10), 2 cases were sexual reversal, and 1 case was 46,X,idic(X;X)(q21.3;q11.1).

Sixteen cases of rare abnormal karyotype were detected, including complex Tri21 (Figure 1), complex TS (Figures 2–4), partial monomer and partial trisomy (Figures 5), 4p-syndrome (Figure 6), 18q-syndrome (Figure 7), and 5p-syndrome.

Figure 1

Karyotype of 46,XX, der(21;21)(q10;q10),t(1;12)(q43;p12.1),inv(15)(q13q24). The arrows show abnormal chromosomes.

Figure 2

Karyotype of 45,X,inv(9)(p11q13)[72]/46,X,dic(Y)(q11.23),inv(9)(p11q13)[10]/46,XY,inv(9)(p11 q13)[4]. The arrows show abnormal chromosomes. (a) 45,X,inv(9)(p11q13). (b) 46,X,dic(Y)(q11.23), inv(9)(p11q13). (c) 46,XY,inv(9) (p11q13).

Figure 3

Karyotype of 45,X[120]/46,X,r(X)(p22.2q22.2)[12]/46,X,rdup(X)(p22.2q22.2)[4]. The arrows show abnormal chromosomes. (a) 45,X. (b) 46,X,r(X)(p22.2q22.2). (c) 46,X,rdup(X)(p22.2q22.2).

Figure 4

Karyotype of 46,X,idic(X)(p11.2)[92]/45,X[9]/47,X,idic(X)(p11.2),idic(X)(p11.2)[5]. The arrows show abnormal chromosomes. (a) 45,X. (b) 46,X,idic(X)(p11.2). (c) 47,X,idic(X)(p11.2),idic(X)(p11.2).

Figure 5

Karyotype of 46,XY,der(9)t(7;9)(p15;p22)pat. The arrows show abnormal chromosomes. (a) The karyotype of the patient. (b) The karyotype of the patient’s father. (c) The karyotype of the patient’s mother.

Figure 6

Karyotype of 46,XY,del(4)(q33). The arrows show abnormal chromosomes.

Figure 7

Karyotype of 45,XX,der(15;21)(q10;q10)mat,del(18)(q21). The arrows show abnormal chromosomes. (a) The karyotype of the patient. (b) The karyotype of the patient’s mother. (c) The karyotype of the patient’s father.

4 Discussion

Chromosomal diseases are often associated with growth retardation, mental retardation, and multiple malformations of organs, which are congenital diseases caused by chromosome number or structural abnormalities. In our study, 181 cases with abnormal karyotype were detected, and the abnormal rate was 41.51% (181/436), which indicated that chromosomal abnormalities were one of the important causes in children with dysplasia.

Intellectual disability (80.66%, 146/181) and dysmorphology (71.82%, 130/181) are the main clinical symptoms of 181 children with chromosomal abnormalities. As known, Tri21 is the most common chromosomal disorder, which implicated with intellectual disability and dysmorphology. The prevalence of Tri21 ranges from 1/700 to 1/2,000 in different ethnic populations investigated [17]. The cause of Tri21 is related to a variety of factors, such as increased reproductive age in women (>35 years old), degeneration of ovarian function, and genetic susceptibility [18,19]. In our study, 136 cases of Tri21 were detected (31.19%, 136/436), including 89 male and 47 female (1.89:1, 89/47). Among them, 130 cases were standard Tri21 (95.59%, 130/136), 5 cases were Robertson translocation Tri21 (3.79%, 5/132), and 1 case was a chimerical type (0.74%, 1/136), which is consistent with previous studies [20,21,22]. In 136 cases of Tri21, about two-thirds of pregnant women did not receive maternal serum screening for DS, and 16 pregnant women’s results of maternal serum screening for DS were high risk, but they did not receive a prenatal diagnosis. Therefore, enhancing people’s awareness of the importance of prenatal screening and genetic counseling in eugenics may be an important means of reducing birth in children with Tri21. In addition, one case with 46,XX,der(21;21)(q10;q10),t(1;12)(q43;p12.1), inv(15)(q13q24) (Figure 1), which is a rare complex Tri21 karyotype, was detected. So, this case is especially helpful to supplement the karyotype diversity of patients with Tri21.

SDS and short stature are the two other major clinical symptoms of 181 children with chromosomal abnormalities. As known, chromosomal abnormalities are one of the important causes of gonadal dysgenesis and physical retardation. In this study, 28 cases of sex chromosome abnormalities were detected, among which 20 cases were TS, and 5 cases were 46,X,i(X)(q10). The main manifestations of TS patients were immature uterus or no uterus, streak ovary or no ovary, primary amenorrhea, breast dysplasia, and short stature, and the main clinical symptoms of the patients with 46,X,i(X)(q10) were short stature and primary amenorrhea. These results suggested the necessity of two intact X chromosomes in the normal growth and development of a female. A single X chromosome in females randomly becomes inactive, but not all genes on which are transcriptionally silenced. Still, 15–20% of genes on inactive X chromosome remain operative and escape from X inactivation [23]. Moreover, normal female development is supported by a double dose of several specific genes on the X chromosome, such as the short stature homeobox (SHOX) gene, which is located at the Xp22, determines the height [24]. So, the haploinsufficiency of SHOX may be the main cause of short stature in patients. Dysmorphology and short stature caused by an X chromosome abnormality are more sensitive to estrogen before 12 years old. So, these kinds of patients need to receive treatment in the early stage. However, in this study, the average age of the patient with TS was11.94, greater than 6.6, which was reported by Massa et al. [25]. Consequently, the growth and development of children should be highly concerned during the preschool period. In addition, another three rare complex karyotypes were detected. One karyotype was 45,X,inv(9)(p11q13)[72]/46,X,dic(Y)(q11.23),inv(9)(p11q13)[10]/46,XY,inv(9)(p11q13)[4] (Figure 2), the other was 45,X[120]/46,X,r(X)(p22.2q22.2)[12]/46,X, rdup(X)(p22.2q22.2)[4] (Figure 3), and the third was 46,X,idic(X)(p11.2)[92]/45,X [9]/47,X,idic(X)(p11.2), idic(X)(p11.2)[5] (Figure 4).

Chromosome monomer or trisomy is one of the important causes of congenital malformation in children. Monomer 9p is a rare condition accompanied by trigonocephaly, facial dysmorphism, and developmental delay [26,27]. In this study, two cases with monosomy 9p were described. The karyotype of one patient was 46,XY,der(9)t(2;9)(p25;p22)mat, which presented with small ears, low ear position, small jaw, wide breast distance, short chest, long fingers and toes, inability to extend the second joint of the middle finger of both hands, special clenched fist posture (index finger pressed on the middle finger, little finger pressed on the ring finger) [28]. The karyotype of another patient was 46,XX,der(9)t(7;9)(p15;p22)pat (Figure 5). Studies have shown that patients with der(9)t(7;9) are mostly characterized by developmentally delayed psychomotor retardation and generalized developmental deficits (Table 3). In this study, the patient presents as developmentally delayed and psychomotor retardation, according to the previous report.

Chromosome 4q deletion syndrome (4q-syndrome) is a rare condition, with an estimated incidence of 1 in 100,000 and the death rate was about 28% [36,37]. Although the clinical symptoms of patients with 4q-syndrome are complex and diverse (Table 4), through statistical analysis of the clinical symptoms of 101 patients, Strehle et al. found that craniofacial (99%), digital (88%), skeletal (54%), and cardiac (50%) were the most common anomalies [37]. Keeling et al. have reported that the critical region involved in the 4q terminal deletion syndrome may be 4q33 [43]. In this study, we reported a 16-month-old boy with 4q33-qter deletion (Figure 6). The patient presents with cleft palate, micrognathia, sydney line of the left hand, and developmental delay. Our results further support the idea that cleft palate-related genes might be located at 4q33 [43]. In addition, although most patients with 4q-syndrome have de novo deletions, familial cases have been reported, suggesting a high risk of recurrence of 4q-syndrome [47,48]. So, for these patients, prenatal diagnosis is necessary.

Deletion of the long arm of chromosome 18 (18q-) is relatively common among cytogenetic abnormality, which occurs incidentally in approximately 1 in 40,000 live births [49]. 18q-syndrome is characterized by a wide range of phenotypic abnormalities related to the size of the deletion and the position of breakpoints. The common clinical features of the 18q-syndrome are growth retardation, mental retardation, microcephaly, facial dysmorphisms, ear atresia, abnormal bone development, CHD, cerebral white matter abnormalities, and immature myelin formation [50,51,52]. In this study, the patient with a rare karyotype of 45,XX,der(15;21)(q10;q10)mat, del(18)(q21) (Figure 7) presented with mental retardation, unclear diction, facial dysmorphisms, abnormal bone development, the little finger end bending, poor balance ability, and unsteady walking. In addition, the patient also suffered from type I diabetes and Hashimoto’s thyroiditis, which were rarely reported. Therefore, this case is especially helpful in supplementing the phenotypic diversity of patients with 18q.

5 Conclusion

Chromosome abnormality is one of the important causes of dysplasia in children, and prenatal screening and diagnosis could play a great significance in preventing dysplasia in children. In addition, the retrospective analysis of the rare case is valuable for clinical diagnosis and risk assessment of recurrence.