University of Edinburgh
 

Medical Information on Hermansky Pudlak Syndrome

by Dr Andrew Blaikie for VI Scotland

This document is written with the minimum use of medical terms and jargon. It is impossible to avoid all medical terms but where we have used them we have attempted to explain them as clearly as we can. Although the information is intended to describe most aspects of the condition each child is different and there will always be exceptions to the rule. As far as we can determine these pages are true and accurate and have been written in good faith.

What this information is not for

This document is not a substitute for a consultation with a Health Professional and should not to be used as a means of diagnosing a condition.

We hope the information will help you to:

  • Have a better understanding of the condition
  • Know what tests and treatments are normally available
  • Know when to seek professional advice
  • Be able to discuss the condition in a more informed way
  • Make the most of consultations with carers, teachers and health professionals
  • Be reassured and more able to cope

Due to staffing limitations we are not able to offer telephone or email advice to parents of children.

Medical Information on Hermansky Pudlak Syndrome

What we see is made in the brain from signals given to it by the eyes. What we see is in fact made in the brain. The brain makes sight from signals given to it by the eyes.

What is the normal structure of the eye?

The eye is made of three parts.

  • A light focussing bit at the front (cornea and lens).
  • A light sensitive film at the back of the eye (retina).
  • A large collection of communication wires to the brain (optic nerve).

A curved window called the cornea first focuses the light. The light then passes through a hole called the pupil. A circle of muscle called the iris surrounds the pupil. The iris is the coloured part of the eye. The light is then focused onto the back of the eye by a lens. Tiny light sensitive patches (photoreceptors) cover the back of the eye. These photoreceptors collect information about the visual world. The covering of photoreceptors at the back of the eye forms a thin film known as the retina. Each photoreceptor sends its signals down very fine wires to the brain.

The wires joining each eye to the brain are called the optic nerves. The optic nerves join together about halfway between the eyes and the brain and then splits apart again. This join is called the optic chiasm. At the optic chiasm about half of the visual information in each optic nerve swaps over to the opposite nerve. This swap makes it easier for the brain to make sense of all the visual information. The information then travels to many different special 'vision' parts of the brain.

All the parts of the brain and eye need to be present and working for us to see normally.

What is Hermansky Pudlak syndrome?

Children with albinism who also have problems with bruising easily, diarrhoea or shortness of breath may have this condition. It is a type of albinism. It is named after the two researchers who first described the condition in the 1950s.

What is Albinism?

The colour of our skin depends on how much melanin is in it. Melanin is a dark brown material (pigment) found in many parts of the body. The body parts that it helps colour include the skin, hair and eyes. Some children cannot make as much melanin as others and some cannot make any melanin at all. They may have pale skin and blonde hair with light coloured eyes. These children have Albinism. They usually also swap less information at the optic nerve join (chiasm) than normal. This can affect the way they see. Children are born with Albinism. They cannot 'catch' it in later life.

Why are some children born with albinism?

Albinism is caused by a misprint in a child's genes. Genes are a chemical alphabet stored in the body. Genes contain the body's 'built-in' plan to make sure all the parts of the body work correctly. A child with Albinism has often been passed (inherited) a gene with a misprint in it from one or both parents. In albinism, because a gene is misprinted, a special chemical called an enzyme does not work correctly. The enzyme is needed to help make melanin. Children with Albinism either don't have as much of the enzyme that helps make melanin or they have none at all. This leads to parts of the eyes being paler than usual. This can cause visual impairment.

The gene that is misprinted may causes other difficulties for the child. These include:

  • Tendency to nose bleeds and easy bruising
  • Diarrhoea and shortness of breath

If a child also has these problems they may have Hermansky Pudlak syndrome. Not all children with this condition will have all these difficulties. Some may only have mild bruising while others may have more marked bleeding. The amount of pigmentation may vary as well.

Why are children prone to bruising?

The misprinted gene also affects the way blood clots. Tiny particles in blood, called platelets, usually clump together to plug up damaged blood vessels in cuts and scrapes. In children with Hermansky Pudlak syndrome the platelets do not work so well. This means that a small scratch can take longer to stop bleeding or a minor bump can develop into a large bruise. The use of aspirin or similar drugs can make the bleeding problem worse.

Why do children develop diarrhoea and shortness of breath?

The body is made up many different parts such as skin, bone and muscle. All the different parts of the body are made up of 'cells'. Cells are tiny factories making materials that the body needs to work and grow. Cells also break down and get rid of any material the body does not need. In Hermansky Pudlak syndrome a material called 'ceroid' builds up in cells. The build up of ceroid causes inflammation and scarring. The bowel and lungs are more prone to damage than other parts of the body. This leads to lose bowel motions, sometimes with blood and shortness of breath.

How does Albinism affect the way a child sees?

Albinism can affect vision in different ways in different children. Generally the less melanin pigment in the iris and retina of the child, the poorer their vision is. Some children may see very well while others may only see bright lights and large shapes. In Albinism it is usually only the central vision that is poor. The vision around the sides is often fine. Because of this, although many children with Albinism have difficulty seeing small letters, most have no difficulty seeing to get around.

In children with Albinism the iris is usually pale and thin with gaps in it. Because of this more light than usual gets into the eye. The extra light that gets into the eye scatters around the inside causing blurred vision. Because too much light enters the eyes, children with Albinism nearly always dislike bright light. This is called photophobia.

The eyes of children with Albinism tend to make fast to-and-fro movements. This is called Nystagmus. Because the eyes are constantly moving, like camera shake, this may also lead to blurred vision. Children with Albinism often need spectacles to help see more clearly. Children may also later develop a squint or a lazy eye.

If you would like more information on these conditions please ask us.

How is Hermansky Pudlak Syndrome diagnosed?

Because the eyes, and often the hair and skin, are paler than normal a diagnosis of albinism can usually be made quite easily. An ophthalmologist or paediatrician can examine the child and confirm the diagnosis. If there is no family history of Albinism and the child is only mildly affected other tests can be done to help make a diagnosis. These include special electrical tests or scans of the head.

If a child with albinism also shows easy bruising or unusual bleeding then they may have Hermansky Pudlak syndrome. Standard tests of blood clotting and bleeding times may however be normal. Experts suggest that the most accurate test is to examine platelets using an instrument called an electron microscope. In Hermansky Pudlak syndrome the platelets can look empty. There is also a blood test that measures how 'sticky' platelets are. This is also useful.

Because health professionals cannot easily diagnose Hermansky Pudlak syndrome with standard blood tests, it is important to promote awareness of the syndrome.

Is there any treatment for Hermansky Pudlak syndrome?

At present there are is no way of fixing misprinted genes. There are many things that can be done to help children with Hermansky Pudlak syndrome though.

Children with albinism and their parents should have an understanding of Hermansky Pudlak syndrome. They should be aware of its possibility. Prolonged bleeding can complicate any operations, even minor dental procedures. Aspirin, products containing aspirin, and any other similar drugs should be avoided. They affect platelets stickiness and can make bleeding worse.

Nosebleeds should be taken seriously. They may become chronic with serious loss of blood. Nasal packing should only be done under medical supervision as removal may cause further bleeding. There may be benefits from treating coughs and chest infections earlier. Smoking should also be avoided. Minor cuts should be treated with Vaseline gauze and pressure dressings. This will minimise bleeding and speed up healing.

What can be done to help vision?

There is no known way to help children make more melanin. Lots of things can be done though to help children with Albinism fulfil the potential of their vision.

We use our vision to get around, learn new things and to meet other people and make friends. It is important to consider what your child's particular problems with vision might be now and in the future.

Bright light often causes discomfort and reduced vision (photophobia). A sunhat and sunglasses may help reduce symptoms of photophobia. Special lenses that get darker in brighter light (photochromic lenses) are useful. Sun block cream should be rubbed into paler, exposed skin to avoid sunburn.

If your child has been prescribed spectacles, contact lenses or a Low Visual Aid (LVA) it is important that they are encouraged to wear and use them. This will help your child see more clearly, reduce glare and ensure the vision parts of the brain grow and develop.

Problems at school may be due to some of the reading books being hard to see. This often means it takes longer and more effort to do the work. If the size of print is increased and letters and words spaced more widely most children will find schoolwork easier. Good bright lighting and crisp black print on a clean white background will also make things easier. Sometimes placing reading books on a slope, which tilts the print towards the child, will improve reading speed as well. When reading it can be helpful to read one line at a time through a 'letter box' placed over the page. Placing a piece of blue tack below the line they are reading, at the beginning of the next sentence, can help some children find their way back to the start of the next line more quickly.

It is also worth watching carefully to find out what the smallest toys are that a child can see and play with. Then try to only play with toys that are the same size or bigger. Placing one toy on a plain background will often help children see it more readily. Placing lots of toys of different size and colour close together on a patterned background can make them 'invisible' to many children with poor vision.

Recognising facial expressions can often be difficult. It is worth trying to find out at what distance facial expressions can be seen and responded to. Then always try to talk and smile from within this distance. This helps a child to learn what facial expressions mean and to copy them.

Infants and young children need to learn about the world around them. Home visiting teachers, physiotherapists and occupational and speech therapists may all add to the child's care and education. It is important to continue the programmes that they recommend. If the child is involved in family activities vision can improve and new skills can develop.

Even if a child has very poor vision many useful and practical things can be done to improve the ability of the child to get around, interact with other children and learn.

Support

Support from parents and counsellors with experience of Albinism can also be helpful. The Albinism Fellowship is a UK based support group that can be contacted using the details below.

Albinism Fellowship
P O Box 77
Burnley, Lancashire,
BB11 5GN
Website: http://www.albinism.org.uk
Telephone - 01282 771900

There is also a specific Hermansky Pudlak support group:

Hermansky-Pudlak Syndrome Network UK
Email: info@hpsnetwork.co.uk
Website: http://www.hpsnetwork.co.uk/

Who wrote these documents?

These pages are the consensus of opinion of many different people. They include parents of visually impaired children, visually impaired children themselves, Community Paediatricians, Ophthalmologists, Educationalists and Psychologists.

The main author and person responsible for their content is Dr Andrew Blaikie who was an Ophthalmology Research Fellow with Visual Impairment Scotland and is a member of the Royal College of Ophthalmologists.

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