Trisomy 13: Changing Perspectives

Dissection of a Down syndrome-associated trisomy to separate the gene dosage-dependent and -independent effects of an extra chromosome

As an aneuploidy, trisomy is associated with mammalian embryonic and postnatal abnormalities. Understanding the underlying mechanisms involved in mutant phenotypes is broadly important and may lead to new strategies to treat clinical manifestations in individuals with trisomies, such as trisomy 21 [Down syndrome (DS)]. Although increased gene dosage effects because of a trisomy may account for the mutant phenotypes, there is also the possibility that phenotypic consequences of a trisomy can arise because of the presence of a freely segregating extra chromosome with its own centromere, i.e. a 'free trisomy' independent of gene dosage effects. Presently, there are no reports of attempts to functionally separate these two types of effects in mammals. To fill this gap, here we describe a strategy that employed two new mouse models of DS, Ts65Dn;Df(17)2Yey/+ and Dp(16)1Yey/Df(16)8Yey. Both models carry triplications of the same 103 human chromosome 21 gene orthologs; however, only Ts65Dn;Df(17)2Yey/+ mice carry a free trisomy. Comparison of these models revealed the gene dosage-independent impacts of an extra chromosome at the phenotypic and molecular levels for the first time. They are reflected by impairments of Ts65Dn;Df(17)2Yey/+ males in T-maze tests when compared with Dp(16)1Yey/Df(16)8Yey males. Results from the transcriptomic analysis suggest the extra chromosome plays a major role in trisomy-associated expression alterations of disomic genes beyond gene dosage effects. This model system can now be used to deepen our mechanistic understanding of this common human aneuploidy and obtain new insights into the effects of free trisomies in other human diseases such as cancers.

Neurosurgical Evaluation and Management of Patients with Chromosomal Abnormalities

Patients with chromosomal abnormalities are at risk for numerous neurosurgical pathologies, given the broad impact and multisystem involvement of these disorders. Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), Patau syndrome (trisomy 13), Klinefelter syndrome (47,XXY), and velocardiofacial or DiGeorge syndrome (22q11.2 deletion) are particularly associated with neurosurgical concerns. Given the heterogeneity of concerns and presentations, these patients benefit from multidisciplinary care provided by teams familiar with their specific syndrome.

A Six-Year-Old Child With Mosaic Trisomy 13

Trisomy 13 was first described by Patau in 1960. It is a rare genetic disease caused by having an extra copy of chromosome 13. Mosaic trisomy 13 happens when a percentage of the cells are trisomic for chromosome 13, while the remaining cells are euploid. Patau syndrome has a limited survival rate, and most of the carriers die before completing the first year of life. Unlike Patau syndrome, mosaic trisomy 13 is known for longer survival. It is associated with central nervous system malformations, cardiac defects, and psychomotor delay. We report a six-year-old male patient, the third child of a first-degree consanguinity. Born at term via emergency cesarean section due to meconium-stained amniotic fluid and fetal distress. Apgar score nine at one minute and nine at five minutes. Initial examination showed typical dysmorphic features like deep-seated eyes, small palpebral fissure, low set of ears, high arched palate, short neck, and right-hand polydactyly. The diagnosis was made through chromosomal analysis, and it revealed mosaic trisomy 13.

Building trust and improving communication with parents of children with Trisomy 13 and 18: A mixed-methods study

BACKGROUND

Trisomy 13 and trisomy 18 are common life-limiting conditions associated with major disabilities. Many parents have described conflictual relationships with clinicians, but positive and adverse experiences of families with healthcare providers have not been well described.

AIM

(1) To investigate parental experiences with clinicians and (2) to provide practical recommendations and behaviors clinicians could emulate to avoid conflict.

DESIGN

Participants were asked to describe their best and worse experiences, as well as supportive clinicians they met. The results were analyzed using mixed methods.

SETTING/PARTICIPANTS

Parents of children with trisomy 13 and 18 who were part of online social support networks. A total of 503 invitations were sent, and 332 parents completed the questionnaire about 272 children.

RESULTS

The majority of parents (72%) had met a supportive clinician. When describing clinicians who changed their lives, the overarching theme, present in 88% of answers, was trust. Parents trusted clinicians when they felt he or she cared and valued their child, their family, and made them feel like good parents (69%), had appropriate knowledge (66%), and supported them and gave them realistic hope (42%). Many (42%) parents did not want to make-or be part of-life-and-death decisions. Parents gave specific examples of supportive behaviors that can be adopted by clinicians. Parents also described adverse experiences, generally leading to conflicts and lack of trust.

CONCLUSION

Realistic and compassionate support of parents living with children with trisomy 13 and 18 is possible. Adversarial interactions that lead to distrust and conflicts can be avoided. Many supportive behaviors that inspire trust can be emulated.

An 8-week-old infant with trisomy 13: dilemmas for medical decision making

Patau syndrome, trisomy 13, is a rare genetic condition with notable physical and mental characteristics and an average reported lifespan of 9 months. For years, trisomy 13 was regarded as a lethal condition; however, a few infants survive for many years, creating a dilemma for both the medical practitioner and the family in terms of the appropriateness and timeliness of specific medical interventions. Even in the face of severe mental and physical limitations, most families of children with trisomy 13 report their experiences as enriching. Appropriate and timely surgical interventions and medical treatments have been shown to increase survival for some infants. Early palliative care helps to limit physical and emotional suffering, and allow the family to create a legacy that their baby's life had meaning, regardless of how long they survive. We present a case of an 8-week-old infant with trisomy 13 to illustrate some of the medical decision making dilemmas faced by both medical practitioner and the family.