Possible isochromosome 22 leading to trisomy 22

Non-mosaic trisomy 22 and congenital heart surgery using the shared decision making model: a case report

BACKGROUND

Liveborn infants with non-mosaic trisomy 22 are rarely described in the medical literature. Reported lifespan of these patients ranges from minutes to 3 years, with the absence of cardiac anomalies associated with longer-term survival. The landscape for offering cardiac surgery to patients with rare autosomal trisomies is currently evolving, as has been demonstrated recently in trisomies 13 and 18. However, limited available data on patients with rare autosomal trisomies provides a significant challenge in perinatal counseling, especially when there are options for surgical intervention.

CASE PRESENTATION

In this case report, we describe an infant born at term with prenatally diagnosed apparently non-mosaic trisomy 22 and multiple cardiac anomalies, including a double outlet right ventricle, hypoplastic aortic valve and severe aortic arch hypoplasia, who underwent cardiac surgery. The decisions made by her family lending to her progress and survival to this day were made with a focus on the shared decision making model and support in the prenatal and perinatal period. We also review the published data on survival and quality of life after cardiac surgery in infants with rare trisomies.

CONCLUSIONS

This patient is the only known case of apparently non-mosaic trisomy 22 in the literature who has undergone cardiac surgery with significant survival benefit. This case highlights the impact of using a shared decision making model when there is prognostic uncertainty.

Live-born trisomy 22: patient report and review

Trisomy 22 is a common trisomy in spontaneous abortions. In contrast, live-born trisomy 22 is rarely seen due to severe organ malformations associated with this condition. Here, we report on a male infant with complete, non-mosaic trisomy 22 born at 35 + 5 weeks via caesarean section. Peripheral blood lymphocytes and fibroblasts showed an additional chromosome 22 in all metaphases analyzed (47,XY,+22). In addition, array CGH confirmed complete trisomy 22. The patient's clinical features included dolichocephalus, hypertelorism, flattened nasal bridge, dysplastic ears with preauricular sinuses and tags, medial cleft palate, anal atresia, and coronary hypospadias with scrotum bipartitum. Essential treatment was implemented in close coordination with the parents. The child died 29 days after birth due to respiratory insufficiency and deterioration of renal function. Our patient's history complements other reports illustrating that children with complete trisomy 22 may survive until birth and beyond.

Complex cardiac defect, bowing of lower limbs and multiple anomalies in trisomy 22. Ultrasound, post-mortem CT findings with necropsy confirmation

Trisomy 22 is commonly associated with severe intrauterine growth retardation and congenital anomalies. The sonographic identification of a complex cardiac defect and bowing of the long bones associated with multiple structural anomalies add new clinical informations to our knowledge about the prenatal phenotype of trisomy 22. These findings have not been reported previously and are of critical importance as sonographic signs of trisomy 22 may overlap that of trisomy 13-18 and will help clinicians in indicating fetal karyotyping. Prenatal diagnosis of trisomy 22 is essential as trisomy 22 is a lethal condition.

Nonmosaic balanced homologous translocations of major clinical significance: some may be mosaic

The main mechanism proposed for formation of homologous translocations/isochromosomes is mitotic and if this occurs in a chromosomally normal conceptus, mosaicism would be expected to be seen. The lack of mosaicism in published cases of rearrangement (REA) of mitotic origin might be explained by under-detection due to the low level mosaicism for a normal line. Recently it was reported that sex-specific centromere instability in early embryogenesis leads to a female prevalence among individuals with mosaicism for pericentromeric rearrangements. To determine whether carriers of apparent non-mosaic homologous REA could be mosaics for a normal cell line, the sex ratio (male to female ratio) among carriers of balanced and unbalanced homologous translocations/isochromosomes was studied. This ratio was determined to establish if there is a female predominance similar to that seen in carriers of REA with mosaicism. In reviewing the literature, a female prevalence among fetuses with balanced homologous REA and among carriers of unbalanced homologous REA detected prenatally, postnatally and in miscarriages was found. Overall, there were 48 males and 72 females in the collected sample, and this ratio differed significantly from the expected sex ratio of 1.06 (P = 0.0075). There is not a male prevalence among miscarried fetuses, there is no evidence of selection against males in the collected material of this study. The analysis of sex ratios in different variants of trisomy 13 with respect to ascertainment (prenatal diagnosis, miscarriages, liveborn) also does not support an intrauterine selection against males as a cause of a female prevalence among carriers of homologous REA. Thus the data presented in this paper suggests that a proportion of the carriers of balanced homologous REA may have mosaicism for a normal line. Since low level mosaicism for a normal line in a translocation carrier would alter his/her reproductive options, it can be recommended that molecular polymorphic analysis be applied to these cases. This would allow those resulting from meiotic formation to be distinguished from those resulting from postzygotic formation. This latter mechanism may indicate the presence of a mosaicism for a normal line, making further intensive karyotypic analysis advisable. However, additional studies of healthy carriers of homologous REA of chromosome 14 or 15 should not be done. (c) 2007 Wiley-Liss, Inc.

Male pseudohermaphroditism and gonadal mosaicism in a 47,XY,+22 fetus

Trisomy 22 syndrome manifestations include cranial and facial anomalies. Ambiguous genitalia have been described in some fetus, but histological examination of the gonads has been rarely provided. We report here the first case of a male pseudohermaphrodite fetus with non-mosaic full trisomy 22 in amniocytes and presenting with ambiguous external genitalia, testes, and a uterus. In this case, we have further analyzed cytogenetically gonadal and uterine tissues. FISH analyses on paraffin-embedded gonads and uterus indicated the presence of two cell lines: XY and monosomy X, with 22%-50% of uterine cells having monosomy X, while 85%-100% of right and 77%-96% of left testicular cells were XY. The distribution of sex chromosomes observed in these tissues could explain the sexual differentiation observed in this fetus. On the other hand, this phenotype could also have resulted from cryptic anomalies in one or several genes implicated in sexual differentiation. Further evidence is thus needed before identifying the true cause of pseudohermaphroditism in our patient.

Isochromosome 22 in trisomy 22 mosaic with five cell lines

This report describes a full-term male infant with trisomy 22 due to an isochromosome 22. Prenatal diagnosis with amniotic fluid showed two cell lines, one with an isochromosome 22 and the other with a deleted isochromosome 22. Subsequent cytogenetic analyses of cord blood, umbilical cord tissue, and placenta revealed additional cell lines. A normal cell line was found in umbilical cord tissue and two of three placental sites. The newborn had numerous dysmorphic features and died within 48 hrs of birth.

Unexpected survival in a case of prenatally diagnosed non-mosaic trisomy 22: Clinical report and review of the natural history

Over 30 cases of complete non-mosaic trisomy 22 have been reported in the literature in the last 20 years [Crowe et al., 1997: Am J Med Genet 71:406-413]. Twenty-two infants were liveborn with an average life expectancy of four days. Of these, nine survived beyond the first two weeks of life. The life span ranged from minutes to 3 years of age. We report a case of an infant diagnosed prenatally with complete non-mosaic trisomy 22. Options such as aggressive medical/surgical intervention or limiting interventions to symptomatic care including home hospice were discussed openly. Given this information, the family elected to provide minimal supportive measures with pediatric hospice. The infant lived for 2 months with her family before her death. Numerous medical and surgical complications are associated with this disorder. Both the family and the medical team must be prepared for in utero fetal demise, stillbirth, or for limited life expectancy. Proper management, therefore, depends upon an understanding of the diagnosis.