Trisomy 11 means cells carry three copies of chromosome 11 instead of the usual two. A pregnancy with the extra copy in every cell has never been reported to reach birth, and it is thought to end in early miscarriage.1Sonic Genetics. General information about positive NIPT results: Trisomy 11 So when trisomy 11 shows up during an ongoing pregnancy, it almost always involves only some cells, or it turns out to be a false alarm. The same name also covers very different situations: a prenatal finding, an extra piece of the chromosome in a child, and a change in leukemia cells. Each has its own outlook.
What a Positive Trisomy 11 Screen Means and What Comes Next
NIPT (non-invasive prenatal testing) reads fragments of DNA floating in the mother’s blood. Most of the pregnancy’s share of that DNA comes from the placenta, not the baby. An extra chromosome 11 in the placenta can therefore flag the screen even when the baby’s own cells are normal. The test never looks at the baby’s cells directly. It cannot say whether an extra chromosome is in every cell or only some, and that is the question that matters most.
False positives happen.2Sonic Genetics. General information about positive NIPT results: Trisomy 11 The real chance that the pregnancy is affected depends on several factors, including your medical and family history.3Sonic Genetics. General information about positive NIPT results: Trisomy 11 Trisomy 11 is an uncommon finding on these screens, so a flagged result calls for careful follow-up, not for assuming the worst.
Confirmation means testing cells directly, by chorionic villus sampling (CVS) or amniocentesis.4Sonic Genetics. General information about positive NIPT results: Trisomy 11 CVS samples placental tissue, usually at about 10 to 13 weeks. Amniocentesis samples the fluid around the baby, usually from about 15 weeks. Because trisomy 11 is often limited to the placenta, CVS can show the same placental finding, while amniocentesis gives a closer look at the baby itself. After birth, cord blood or a blood sample from the baby can be tested, and after a miscarriage the pregnancy tissue can be tested.5Sonic Genetics. General information about positive NIPT results: Trisomy 11 Ask for a referral to a genetic counselor before making any decision based on the screen alone.
Results from cultured cells can take one to two weeks, so expect a wait. Writing down questions beforehand helps, such as which test to have and what the next scan will check.
A detailed ultrasound during the wait looks for growth problems and structural differences in the heart, brain and other organs. A normal scan is reassuring, but it does not replace a confirming test.
Mosaic and Placenta-Only Trisomy 11 Usually Mean a Healthy Baby
Mosaicism means a mix of normal cells and cells with the extra chromosome. Almost all reported babies born after a prenatal finding of mosaic trisomy 11 developed normally before and after birth, with no trisomic cells found once they were born.6Sonic Genetics. General information about positive NIPT results: Trisomy 11
The individual cases show how this plays out. In one baby, 26% of the cells in the amniotic fluid were trisomic, yet the baby’s own blood was normal, the baby was healthy at birth, and development was normal at 1 year.7PubMed. Amniotic trisomy 11 mosaicism–is it a benign finding? In another pregnancy, one cluster of cells out of 17 grown from the fluid was trisomic, a repeat amniocentesis found 1 trisomic cell in 101, and a healthy baby was born at 38 weeks.8PubMed. Prenatal diagnosis of trisomy 11 in a single colony of cultured amniocytes at amniocentesis in a pregnancy with a favorable outcome
A figure like 26% describes the cells that were sampled, not how severely the baby will be affected. A mix of cells also does not say which tissues hold the trisomic ones, and that location drives the outcome. A laboratory number alone cannot predict a child’s health; repeat tests, scans and the baby’s blood fill in the picture.
High levels of mosaicism in the placenta are linked to poor fetal growth and to pregnancy loss.9Placenta. Confined placental mosaicism and intrauterine fetal development In one reported case, trisomy 11 was found throughout the placenta and the baby’s skin cells were normal, yet the baby grew very poorly in the womb.10PubMed. A case of paternal uniparental disomy for chromosome 11 Extra growth scans later in the pregnancy are expected, even after a reassuring amniocentesis.
If a mix of cells is found, useful questions include:
- Was the extra chromosome seen only in lab-grown cells, or in uncultured cells too?
- Has uniparental disomy been checked?
- How often will growth scans be done?
- Should the baby’s blood be tested after birth?
What Causes Trisomy 11
An extra chromosome usually comes from an egg or sperm cell, or an early embryo cell, that divides unevenly so one cell ends up with an extra copy. Eggs and sperm are made by a division that splits each chromosome pair so every cell receives one copy. When a pair fails to separate, an extra chromosome results. If this happens before conception, the embryo starts with three copies of chromosome 11 in every cell. If the error occurs in a division after fertilization, only the descendants of that cell carry the extra copy, which produces a mix of cells. The timing of the error decides whether the trisomy is in all cells, some cells or the placenta only.
When the parents’ own chromosomes are normal, as in the healthy-baby case described above, the error happened by chance.11PubMed. Prenatal diagnosis of trisomy 11 in a single colony of cultured amniocytes at amniocentesis in a pregnancy with a favorable outcome Errors in cell division are common in early human development and are not caused by diet, exercise, stress or anything done during pregnancy. Chromosome errors in eggs do become more frequent as the egg ages, so maternal age contributes to trisomies in general, though nobody can control it.
Counselors often test the parents’ chromosomes to rule out a rearrangement that can be passed on. Partial trisomies caused by such rearrangements carry a real repeat risk, which the next section explains.
An embryo with trisomy can sometimes drop the extra chromosome.12PubMed Central. Paternal Uniparental Disomy with Segmental Loss of Heterozygosity of Chromosome 11 are Hallmark Characteristics of Syndromic and Sporadic Embryonal Rhabdomyosarcoma If it drops the copy from the wrong parent, both remaining copies come from one parent, which is called uniparental disomy (UPD).13PubMed Central. Paternal Uniparental Disomy with Segmental Loss of Heterozygosity of Chromosome 11 are Hallmark Characteristics of Syndromic and Sporadic Embryonal Rhabdomyosarcoma This matters for chromosome 11 because some of its genes work only when inherited from a particular parent.14PubMed. Uniparental disomy: Origin, frequency, and clinical significance After mosaic trisomy 11 is found, doctors check for UPD, and it was ruled out in both healthy-baby cases above.15PubMed. Amniotic trisomy 11 mosaicism–is it a benign finding?16PubMed. Prenatal diagnosis of trisomy 11 in a single colony of cultured amniocytes at amniocentesis in a pregnancy with a favorable outcome
The UPD test compares DNA markers from the baby’s sample with blood from both parents. No extra procedure is needed for the pregnancy beyond the sample already taken.
Partial Trisomy 11 and Emanuel Syndrome
Here the extra material is in the child’s own body cells, not just the placenta. These children are born and live with ongoing needs, unlike babies with a full trisomy 11. Care is usually managed by a team that may include cardiology, neurology and therapy specialists.
An extra copy of most of the long arm of chromosome 11 brings short stature, developmental delay, distinctive facial features, heart defects, seizures, and kidney, genital and limb differences.17PubMed Central. Molecular cytogenetic characterization of partial trisomy of the long arm of chromosome 11 in a patient with multiple congenital anomalies Smaller extra pieces generally cause milder features.18PubMed Central. Molecular cytogenetic characterization of partial trisomy of the long arm of chromosome 11 in a patient with multiple congenital anomalies An extra piece near the end of the long arm is linked to severe intellectual disability and brain malformations.19PubMed. Phenotype and micro-array characterization of duplication 11q22.1-q25 and review of the literature The features depend on which segment is duplicated and how large it is, so two children can have different findings when their duplicated regions overlap only partly. Doctors describe each child by the exact region found on testing, and families often compare notes with others who share that region.
Emanuel syndrome comes from an extra small chromosome that carries part of chromosome 22 and the end of chromosome 11’s long arm.20PubMed Central. A case with Emanuel syndrome: extra derivative 22 chromosome inherited from the mother Babies have weak muscle tone, slow growth, significant developmental delay and usually severe intellectual disability.21MedlinePlus Genetics. Emanuel syndrome About half are born with a cleft or high-arched palate, and heart or kidney problems can be life-threatening in early childhood.22MedlinePlus Genetics. Emanuel syndrome
The extra chromosome can be inherited from a parent.23PubMed Central. A case with Emanuel syndrome: extra derivative 22 chromosome inherited from the mother A parent can carry a balanced rearrangement between chromosomes 11 and 22 without having any symptoms, because they have all the genetic material they need. They may only learn of it after a child is diagnosed. When that parent makes eggs or sperm, the swapped chromosomes can divide unevenly, and a child can receive the small extra chromosome on top of the normal ones. Most often the rearrangement is carried by the mother, though it can come from either parent, which is why testing both parents is advised. Not every case is inherited; a few arise as a new change in the child, and then the parents’ tests are normal. If a balanced rearrangement is found, future pregnancies can be tested early, and other relatives may want to be tested as well.
An extra paternal copy of the tip of chromosome 11’s short arm causes Beckwith-Wiedemann syndrome, with large birth weight, a large tongue and broad hands.24PubMed Central. Paternally inherited duplications of 11p15.5 and Beckwith-Wiedemann syndrome Children whose syndrome comes from this duplication have intellectual disability more often than children with the syndrome from other causes.25PubMed. Beckwith-Wiedemann syndrome due to 11p15.5 paternal duplication associated with Klinefelter syndrome and a “de novo” pericentric inversion of chromosome Y Chromosomal microarray testing can find duplications too small to see under a microscope.26PubMed. Use of targeted array-based CGH for the clinical diagnosis of chromosomal imbalance: is less more?
Trisomy 11 in Leukemia
In leukemia, the extra chromosome 11 is found only in the bone marrow cancer cells. It is not inherited and is not present in the rest of the body. It is found by bone marrow biopsy and listed among the findings that help classify the leukemia, read together with other lab results.
An extra chromosome 11 as the only abnormality is rare in acute myeloid leukemia and signals a poor outlook.27PubMed Central. Trisomy 11 as an isolated abnormality in acute myeloid leukemia is associated with unfavorable prognosis but not with an NPM1 or KIT mutation In one group of patients, about half went into remission, more than half of those relapsed, and about 1 in 10 were alive at 3 years.28PubMed Central. Adult acute myeloid leukemia with trisomy 11 as the sole abnormality is characterized by the presence of five distinct gene mutations: MLL-PTD, DNMT3A, U2AF1, FLT3-ITD and IDH2 In another group, most patients had disease that resisted treatment or came back, and the one long remission followed a stem cell transplant.29PubMed Central. Trisomy 11 as an isolated abnormality in acute myeloid leukemia is associated with unfavorable prognosis but not with an NPM1 or KIT mutation Because the change is not inherited, family members are not at risk from it and may still be tested as possible stem cell donors.
Useful questions for the cancer team: Are other gene changes present that alter treatment? Is a stem cell transplant an option? Are clinical trials available?
How to Read a Trisomy 11 Lab Report
A karyotype is the count and picture of a sample’s chromosomes, written in a code such as 47,XX,+11. Here 47 is the total number of chromosomes, XX means female, and +11 means an extra chromosome 11. A slash separates cell lines, so in a report such as 47,XX,+1130Sonic Genetics. General information about positive NIPT results: Trisomy 11/46,XX31PubMed. A case of paternal uniparental disomy for chromosome 11, 47,XX,+11 is the trisomic line and 46,XX is the normal line. The number in square brackets is how many cell groups showed that pattern, so one group of cells was trisomic and 16 groups were normal.32PubMed. Prenatal diagnosis of trisomy 11 in a single colony of cultured amniocytes at amniocentesis in a pregnancy with a favorable outcome FISH, a faster test on uncultured cells, reports a cell count such as 1 in 101.33PubMed. Prenatal diagnosis of trisomy 11 in a single colony of cultured amniocytes at amniocentesis in a pregnancy with a favorable outcome
Other terms you may see: “mosaic” means more than one cell line was found. Normal parental chromosomes point to a chance event rather than an inherited rearrangement. “UPD excluded” means both copies did not come from one parent. Microarray results list duplications by chromosome region, such as 11q.
Ask the genetic counselor to go through the report line by line, request a copy for your records, and ask whether any finding needs testing after birth.
Support for Families of Children With Rare Trisomy Conditions
The daily medical and basic care needs of children with rare trisomy conditions often lead mothers to stop working outside the home.34International Journal of Developmental Disabilities. Examining In-Home Care Needs and Work Responsibilities for Parents with Children with A Rare Trisomy Condition Parents frequently cut their hours, partly because suitable caregivers are hard to find.35International Journal of Developmental Disabilities. Examining In-Home Care Needs and Work Responsibilities for Parents with Children with A Rare Trisomy Condition Many parents find strong support from their partner but more difficulty with grandparents and extended family.36PubMed. ‘We’ve been through it all together’: supports for parents with children with rare trisomy conditions Plan early for help with care and for changes to work arrangements.
Rare chromosome support groups connect families facing the same diagnosis. Early intervention services can provide therapy at home, and social workers can help with benefits and finding respite care.
On work and money, ask early about leave, flexible hours or remote work, since needs can change as a child’s health does. Public benefits and disability programs may help with costs of equipment, therapy and care, and a social worker can explain what applies locally. Caregivers can be trained in the child’s specific needs, such as feeding or seizure care, ahead of time so that a break becomes possible.