Mosaicism
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Mosaicism Involving Sex Chromosomes
What is Mosaicism?
- Mosaicism is a term that refers to people who have two or more genetically different sets of cells in their body.
- When this involves sex chromosomes this is considered an innate variation of sex characteristics.
- Mosaicism affects only the parts of the body that it exists in, and how it is expressed in a person’s physical traits varies from person to person.
- This means that mosaicism doesn’t describe any one single type of innate variation of sex characteristics and can co-exist with, or underpin, other variations.
- Unless it presents with noticeable characteristics, mosaicism might not be detected. This means that mosaicism may be surprisingly common in the human population.
- A common example that is not an intersex variation is heterochromia, where someone has two different coloured eyes with each eye having different genes.
Where Does Mosaicism Come From?
- There are a number of ways that mosaicism can occur, though they are all a product of complex genetic processes.
- Because mosaicism is used to describes two or more different sets of genetic material in an individual, the mechanisms that produce this are both varied and specific
- Most forms of mosaicism are the result of random genetic processes.
Anaphase Lag
- The most common cause of mosaicism
- This is when a chromosome is lost during initial cell division in a fertilised egg, producing one cell with 1 chromosome and another cell with the usual pair (instead of both cells receiving a pair)
- As the cells continue to divide, two genetically distinct populations of cells emerge, forming the developing embryo, and eventually, an individual with both sets of genetic material.
- If this involved the sex chromosomes it may mean that some chromosomes are “45, X0” and some are “46, XX” (this is also termed Mosaic Turner Syndrome)
Mitotic Nondisjunction
- This occurs when chromosomes do not separate in a typical way in a replicating cell.
- This produces a cell with 1 chromosome and another cell with 3 chromosomes, instead of each cell receiving a pair).
- As these cells replicate, two or more genetically distinct cell populations emerge.
- If this involved the sex chromosomes it may mean that some chromosomes are “45, X0” and some are “47, XXY” (also termed Mosaic Turner and Klinefelter Syndrome).
Endoreduplication
- This occurs when a cell duplicates its chromosomes in preparation for producing new cells, but does not divide into new cells.
- When it does replicate it produces a cell with more the usual chromosome pair and another cell with 3 or more sets of the chromosome.
- If this involved the sex chromosomes, it means that some chromosomes are “46, XY” and some are “47, XYY” (also termed Mosaic XYY Syndrome).
Chimerism is a variation similar to mosaicism where two or more genetically different populations of cells exist in the body. Instead of this occurring from cellular replication like mosaicism, chimerism occurs through the fusion of two different genetic sources. This can happen when two embryos that would otherwise develop as twins, fuse together to produce a single embryo.
In all these instances, a variation of sex characteristics occurs based on which genes are present in which parts of the body and how they interact with hormones. The proportions of cells with different chromosomes can also vary throughout different tissues in the body. This can produce a range of diverse effects depending on the proportion of cells and their location. For example, a low ratio of different cells in the heart has a very different impact to a high proportion of different cells in the gonads.
As a result mosaicism has a much higher degree of variability than most other innate variations of sex characteristics. For example, non-mosaic 45,X0 (Turners) or 47,XXY (Klinefelter) present with only some variations in sex characteristics. Mosaicism or chimerism can also be the cause of an Ovotesticular variation or gonadal dysgenesis where two different populations of cells emerge during the development of gonads.
Recognising Mosaicism
Mosaicism can be difficult to recognise due to its highly variable presentations. It is typically observed when a person is diagnosed with another intersex variation. For example you may be diagnosed with Turner Syndrome, which is present with mosaicism in 30-40% of all cases.
The highly variable nature of mosaicism, means that indicators and signs will be highly specific to the type and degree of mosaicism.
Some common indicators of mosaicism may include:
- Variation in skin, hair, or iris pigmentation.
- Anatomical variations and asymmetry.
- Other variations of sex characteristics.
Health Considerations
Most people with mosaicism live full, happy, and healthy lives. However, you should work with your doctor to understand how mosaicism affects your body and consider if there are any health concerns that need to be monitored or understood. Your health needs should be understood in relation to your specific variation/s and mosaicism.
Depending on where mosaicism is found in the body, there can sometimes be an increased risk of cancer. This is particularly true for people with a Y chromosome.
If an increased cancer risk is something that impacts you, then there may be a need for regular testing or monitoring. This is best discussed with your doctor as risk factors are individual and specific to the nature and type of mosaicism you have.
As with all innate variations of sex characteristics, these differences can be understood and managed allowing people to live fulfilling lives. There are also a range of treatments available to address and manage these conditions should they arise. We need to be able to understand our bodies to be able to look after ourselves, and there is nothing inherently shameful about how your body exists.
Treatment Considerations
You can speak with your doctor about your options should you wish to address or manage any aspect of your variation. It is also perfectly acceptable not to opt for any intervention or medical management.
The Australian Human Rights Commission recommends minimal medical intervention for people with intersex variations until a person is of an age to consent to treatment, unless there is a clear medical reason to intervene. You should be supported to make the decisions that are best for you.
Talk with a doctor you trust to establish a healthcare plan that is individualised to your needs. Your healthcare plan might include regular check-ups, any required regular testing or health screening, and medications that you may need. It is important that your doctor or health provider listens and responds to your preferences, explains the benefits and risks of any treatment they propose, and provides information about any alternative available options, including the decision to not undertake treatments.
Treatment and Gender
Some treatment pathways are predicated on the idea that it is preferable to make bodies fit stereotypical characteristics as much as possible. Different assumptions are placed on the gender identity of people with mosaicism depending on your anatomy and your sex of rearing.
Typical assumptions centre around the idea that people will identify as girls/women or boys/men in line with their anatomy and sex of rearing. While this may be true for many, or even most people, and these assumptions exist, it is important to remember that people understand themselves in many different ways, and all understandings are equally valid.
It is important to take some time to consider your options, feelings and identity before proceeding with any non-urgent medical options. Access to psychosocial support, peers and community can help you to understand these options.
Hormone Replacement Therapy
If your body can not or does not produce enough sex hormones such as estrogen or testosterone, you may need to start or continue hormone replacement therapy, especially if you experience some of the impacts of low sex hormones.
All bodies require a balance of estrogen and testosterone, amongst other sex hormones. Impacts of low sex hormones can include:
• Loss of bone density, which can lead to osteoporosis. Osteoporosis causes the bones to become brittle and more vulnerable to fractures and broken bones.
• Impaired cognition.
• Low mood.
• Low sex drive.
• Fertility challenges.
Some people may like to take supplementary hormones to help with some of these issues. The benefits of hormonal therapy can include:
• Maintaining bone health.
• Initiating, progressing or altering puberty.
• Alleviating low mood or personal distress.
• Increasing sex drive (if this is beneficial for you).
People can respond in different ways to different hormone treatments. Therefore, you and your healthcare provider should understand and manage the side effects and consequences of undergoing hormone replacement.
These are decisions that you should make for yourself based on how you understand your preferences, identity and body, alongside an awareness of all potential challenges and side effects that come with hormonal therapies.
Importantly not all people with mosaicism want or need hormone replacement therapy.
Counselling and peer support can help determine the best decision for you.
Surgical Interventions
Most people with mosaicism will not require surgical interventions. Where there are genuine health risks this should be addressed in an appropriate time frame as determined by the treating medical team/specialists.
Unnecessary surgery causes additional stress and may need to be followed by more treatments and surgeries later in life. These surgeries are intrusive and are often harmful to physical sensation and sexual enjoyment later in life and take away decision-making and options from the individual, who may grow up to understand their identity and values in ways that are incongruent with the proposed treatment/s. They may be illegal in some jurisdictions in Australia.
Genital Surgeries
Some genital surgeries may sometimes be necessary for physical health and wellbeing. These may include addressing a blocked or obstructed vagina, urethra, or a vulva that does not allow urine, vaginal discharge, or menstrual blood to drain safely. These present genuine health risks to an individual and should be addressed appropriately.
Other surgeries may be suggested in infancy or childhood often to change or alter genital appearance (such as clitoral surgeries and labiaplasties) or function to fit gender stereotypes (such as penile surgeries and vaginoplasties). These kinds of treatments are largely proposed for social reasons and do not address any medical need.
It is best to defer these decisions until an individual is old enough to be involved in decision-making and consent to treatment. Sometimes these surgeries may be described or referred to as a ‘correction’ or using other similar language. This presumes that something needs to be ‘fixed’ when in reality the tissue is healthy and functional. Interventions proposed without clear evidence of urgent medical necessity may be illegal in some jurisdictions in Australia.
Gonadal Surgery
Undescended testes may be relocated to the scrotum, if you have that anatomy. This is called an orchiopexy. Relocating the testes can potentially improve fertility as the internal body temperature is much higher and associated with reduced fertility. In some cases, relocating the testes may also assist with testosterone production, however this is not guaranteed.
If you don’t have a scrotum or opt not to have your testes relocated outside the body you may choose to leave them where they are or choose to have them removed when you can provide fully-informed consent.
Fertility Treatment
Fertility can be challenging or distressing for many people with mosaicism.
Your fertility will depend on your variation and anatomy. If having children is important to you, and you experience difficulty with your fertility you may wish to consider options that utilise Assisted Reproductive Technologies.
Fertility concerns should ideally be raised with a doctor early if you are considering having children. Where possible, your doctors can guide you through your options and any steps or decisions you may need to make.
You may also wish to explore alternate family-building options. Parenting takes many shapes and forms such as adoption, step-parenting, foster care, parenting pets, being a godparent or playing an active role with nieces, nephews or cousins. Life is rich with opportunities to nurture, care for and provide guidance to others. Our families can be the ones we are born with but also the ones we choose for ourselves. This can include choosing to have a family without children.
When making any decisions about starting a family, take time to consider your view on your role you want to play in your family and acknowledge the impact of social pressures to conform to traditional ideals about parenthood.
Health Monitoring and Other Treatments
Examinations and Photography
You may need to undergo regular examinations to understand how your body is functioning. This includes genital examinations. Ask how these can be reduced in number, or if they need to go ahead at all.
If you are a parent or carer, you may be asked if photographs can be taken of your child’s genitals, this is not usually necessary, so it is important to ask why it is being suggested. This is sometimes done to minimise the need for future genital examinations, however, should be fully considered due to the distress they can cause the individual later in life. These photographs will not be distributed without your explicit consent as the parent/individual. If you’re uncomfortable with a decision your parents made, you can ask for the photographs to be destroyed.
You can choose not to have genital examinations, or photography altogether, and may wish to ask whether the doctor is able to get the same information another way. More guidance on paediatric genital examinations and photography is available at https://www.rch.org.au/endo/for_patients_and_families/Information_
about_genital_examinations/
As an adult, your permission must be sought to be examined by doctors, or medical students for education purposes. You should not feel compelled to agree.
Ongoing Care
You may see many different kinds of doctors and health workers. Some people that may be involved in your care may include:
- A psychologist or psychiatrist, who can help you consider your own treatment options, your wishes and support you and your family.
- A social worker, peer navigator and peer support workers who can help you navigate health systems, connect you with community, and address any challenges.
- Your general practitioner or family doctor.
- An endocrinologist (to help with any hormonal management).
- A gynaecologist (for anything to do with your anatomy, menstruation or sex).
- A urologist (for anything to do with your anatomy, bladder or urination).
- Surgeons involved in your care.
- Fertility specialists (for any fertility support or assisted reproduction).
- Sexual health specialists.
- Pelvic health physiotherapists.
- Sexologists and sexological bodyworkers.
You can ask your regular doctor about creating a care plan, and for referrals to community/peer support organisations. Other people have been through these circumstances before, and they can help you navigate medical and support systems.
If you are maintaining healthy hormone levels, and your body is functioning and developing in ways that you are happy with there is likely no need for any medical interventions. As always you should ask for written copies of the latest reports on outcomes so that you can access all the information about your body and health if and when you need access to it. It’s important for everyone to have adequate information about their body in order to best manage their physical and mental health.
Working with a doctor is important to understand which of these health concerns are relevant to your body. Learning how to monitor and manage these conditions is an important aspect of living with mosaicism
Community and Other Supports
Many people have mosaicism and some are public about it.
Although mosaicism may be different to other innate variations, the many struggles faced from the medical community and society more generally, are universally experienced by the intersex community. There are great benefits in connecting with people with mosaicism, and also with people who have other innate variations.
Supports Available for Individuals and Families in Australia
- InterLink psychosocial support service – https://ilink.net.au
- IHRA Intersex Human Rights Australia (formerly OII Australia) – https://ihra.org.au/
- IPSA Intersex Peer Support Australia (formerly AISSGA) – https://isupport.org.au/
References
Tyl H. Taylor, Susan A. Gitlin, Jennifer L. Patrick, Jack L. Crain, J. Michael Wilson, Darren K. Griffin
The origin, mechanisms, incidence and clinical consequences of chromosomal mosaicism in humans, Human Reproduction Update, Volume 20, Issue 4, July/August 2014, Pages 571–581, https://doi.org/10.1093/humupd/dmu016vb
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