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Trichothiodystrophy (TTD) - testing and diagnosis


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Trichothiodystrophy (TTD) is a very rare and life limiting condition, passed on by parents. It is diagnosed with straightforward tests that will look at your child's genes. You may need to wait several months for results, as the genetic testing is extremely complex. If your child is diagnosed with TTD, you will get lots of support to help with your child's condition and symptoms. 

What is trichothiodystrophy (TTD)?

TTD is a very rare, genetic condition. Both parents must pass on the faulty gene for a child to be affected. Only 1 child in a million will be affected with TTD.

Having genetic tests for TTD

These tests are done to confirm if your child has TTD, by taking samples which are looked at to see if there is a change in the gene that causes TTD. Hair strands are checked to see if there is any 'tiger tail banding'. This can be an indicator of TTD. These are unique tests, available on the NHS, and have been specially developed to support the National TTD Service.

Blood test

Your child will need to have a simple blood test. The genetic testing is extremely complex and can take up to 6 months to be completed. The test may need to be repeated on a new sample of blood if the results are unclear.

Skin biopsy

Your child will need to have a small piece of skin (about 2mm) taken from their buttock. This will be done with a local anaesthetic so it should not hurt once the area has been numbed. A small stitch may be needed to close the wound.

The skin sample will be sent to the lab where they will grow more cells. Genetic testing will then be done on these cells. It takes about 3 months to get the results of this test.

Hair strand microscopy

A small amount of hair will need to be taken. It is not necessary to take the root of the hair so this will not be painful.

The sample is then tested. The result of this test can take up to 2 months to be received.

Understanding basic genetics and TTD

Genes come in pairs. One gene comes from the mother and the other from the father. Both genes from each parent must be affected to cause the disorder. People with only one affected gene in their pair are called carriers and they do not have the condition. However, they can pass the affected gene on to their children.

If you are born to parents who both carry the same affected gene, you have a 1 in 4 (25%) chance of inheriting both affected genes and developing the disease. You also have a 1 in 2 (50%) chance of being a carrier for the condition, and a 1 in 4 (25%) chance of not being affected at all.

Follow-up appointment

You will be informed by letter of the results. If your child does not have TTD you will be referred back to the care of your GP or referring doctor. If your child does have TTD you will be invited to be seen by the National TTD Service.

A diagnosis of CS can mean you and your family have lots of questions. When your child is diagnosed there is often a lot of information to understand. 

How TTD can affect your child

TTD is a life-limiting condition. There is no specific life expectancy, as it will depend on the severity of your child’s condition.

TTD has some physical characteristics which are often similar across many affected patients.

  • Height – this will depend on the severity of their condition.
  • Brittle hair and nails – these will flake and break easily.
  • Ichthyosis (thick, dry skin) – your child will shed skin at a faster rate than usual and will need a regular moisturising routine.
  • Your child may have congenital (from birth) cataracts – these are often surgically removed.

Your child’s hearing and sight may be affected. This can often be managed with glasses and hearing aids.

People with TTD are more at risk from tooth decay, so particular care needs to be taken with oral hygiene and making sure that a healthy diet is followed.

A reduced immune system is also a common problem for patients with TTD. This means that patients are more likely to get infections, so extra care needs to be taken, especially during the winter months when there is an increased risk of chest infections.

Your child may have problems with eating and drinking. These can be managed in several different ways ranging from thickening oral fluids, to a gastrostomy (a feeding tube into the stomach). The options will depend on the advice of the doctors.

Photosensitivity (sensitivity to the sun) and photophobia (sensitivity to light) can be an issue for patients with TTD. High factor (50+) sunscreen should be used if they are going out but, where possible, you should try to keep your child in the shade. Make sure that sunshades are used on car windows, where appropriate. In severe cases, special film will need to be placed on the windows at home and in the car to make sure that no UV is present. Sunglasses will be necessary, maybe even indoors, if your child suffers with photophobia.

TTD will have an impact on your child’s developmental abilities. You may have noticed that they are not reaching their milestones at the same rate as other children. This will become more apparent as they get older.

As with many other illnesses, there is a spectrum (range). Patients with TTD will all have very similar attributes, but the severity of the condition will vary depending on how the genes are affected.

How your child’s symptoms and condition will be managed

In order to manage all of your child’s symptoms there will be many different professionals involved. Each professional will have a different role in making sure that your child is kept as well and comfortable as possible.

Locally, your child should have a paediatrician and a community nursing team (where appropriate) alongside your GP, dentist and health visitor/school nurse.

You will have the option to be seen each year with your child at the multidisciplinary TTD clinic at St Thomas’ Hospital. This will give you the opportunity to see a range of specialist consultants in TTD genetics, dental, dermatology (skin), neurology (nerves), ophthalmology (eyes), dietetics (nutrition), occupational therapy, and clinical psychology. These specialists will communicate with your local teams. If your child is unwell or needs more monitoring or intervention, you will be referred back to your local team. You may be asked to come to the multidisciplinary clinic at St Thomas’ sooner than your usual yearly appointment.

As well as these specialists, you will see your TTD nurse practitioner at clinic. They will support you and your family, and oversee your local care, making sure that all services are in place. They will also work with you to undertake a comprehensive nursing assessment and put in place emergency care plans. You will be offered a yearly home visit with the TTD nurse as well as telephone and email support.

Depending on your child’s symptoms they may also have a local dermatologist, ophthalmologist, dietitian, physiotherapist, occupational therapist, or speech and language therapist.

How TTD affects you and your family

Having a child with TTD will change your life. The journey you have will be challenging, but you don’t need to face it alone. The National TTD Service will support you with home visits, telephone support and multidisciplinary clinics, as well as liaison with your local services to make sure that they know how to care for your child and their condition.

Recessive genetic conditions and your future

Having this genetic information may change your life decisions and you may need to think about this carefully, for example, if you are considering having more children.

Parents who are closely related to each other, such as first cousins, are more likely to have children with recessive conditions. This is because they are more likely to share some of their genetic information and carry the same faulty genes. This is the case for all recessive conditions, not just TTD.

If your child has TTD you will be offered the opportunity to have genetic counselling.

Useful sources of information

If you have any questions or concerns about TTD, please call the TTD administrator on 020 7188 7188, extension 58030, Monday to Friday, 9am-5pm.

National TTD Service

The National TTD Service is a rare diseases specialist service funded by NHS England and is based at Guy's Hospital. The service works closely with patients and their local health authorities to provide the best coordinated care for people with TTD.


Amy and Friends Support Group

The support provides funding to attend clinic, where it is needed, and runs a yearly conference for families and medical professionals, as well as providing ongoing support and activities.

Amy and Friends website 



Ref number: 5089/VER1 and 5090/VER1

Date published: October 2020 | Review date: October 2023

© 2020 Guy’s and St Thomas’ NHS Foundation Trust

A list of sources is available on request


Where next?

Contact us

If you have any questions or concerns about CS, please contact the CS administrator.

Phone 020 7188 7188 (extension 58030)

Monday to Friday, 9am to 5pm.

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