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What do you need to know about your child’s peroxisomal biogenesis disorder-Zellweger spectrum disorder (PBD-ZSD)? know

Defining PBD-ZSD

It is 1 disease, but it has a spectrum of severity

Until recently, PBD-ZSD was viewed as 3 separate diseases, but we now know it is a set of disorders that form a spectrum, or continuum, of 1 disease. This spectrum can range from mild (infantile Refsum disease, or IRD), to moderate (neonatal adrenoleukodystrophy, or NALD), to severe (Zellweger syndrome, or ZS).

These disorders are caused by a loss of function in important parts of your cells called “peroxisomes,” which can affect many parts of the body–from the eyes to the liver. Learn more about how it works here.

As a spectrum, PBD-ZSD will affect each patient differently. How the disorder affects patients depends on their age when PBD-ZSD symptoms first start to appear.

No matter where someone is on the PBD-ZSD spectrum, the impact is serious and lifelong, and it needs to be monitored consistently.

You are your child’s champion—know how their PBD-ZSD is affecting them

What to watch out for when your child has PBD-ZSD

How and when PBD-ZSD affects different parts of the body can vary widely

PBD-ZSD affects each person differently. Monitor your child for any changes to his/her symptoms, so you and your child’s healthcare team can provide timely care.

Not all changes to your child’s health can be easily noticed, so going to routine checkups with different specialists is very important

How do ZSDs affect different body systems and functions?

Nutrition and growth

Hearing

Vision

Neurological

Liver

Kidney

Hormone levels

Bone

Teeth

Control of movement

Children with PBD-ZSD may experience malabsorption

Signs and symptoms

Poor growth
Feeding problems
Deficiency in fat-soluble vitamins (which dissolve and are stored in fat in the body)

Background

Low levels of bile acids lead to poor absorption of nutrients into the bloodstream and a deficiency in fat-soluble vitamins.
Currently, there is no specific diet recommendation for people with PBD-ZSD.
Children with PBD-ZSD are often very picky about what they will eat.
Severely reduced muscle tone often contributes to feeding problems. In more severe cases, some infants may be unable to suck or swallow.

You are your child’s Champion—learn how to best manage their condition

Some degree of hearing loss is common in children with PBD-ZSD

Signs and symptoms

Hearing loss
Abnormal shape of ears
Ears rotated further back

Background

Deafness is nearly universal in children.
In infants, deafness is typical, but not always noticed right away.
Teens and adults often have some form of hearing loss.
Hearing should be evaluated every year.

You are your child’s Champion—learn how to best manage their condition

Some degree of vision loss is very common in people with PBD-ZSD

Signs and symptoms

Vision loss
Spots on or around the iris
Cataracts (when the lens of the eye is cloudy)

Background

Vision loss from damage to the retina (the tissue at the back of the eye) is among the most common symptoms in people with PBD-ZSD.
Cataracts can blur vision but are less common.
Glaucoma and other issues with the retina may develop in severe cases.

You are your child’s Champion—learn how to best manage their condition

PBD-ZSD often affects the nervous system

Signs and symptoms

Developmental delay in mental and/or physical abilities
Seizures, most often seen in newborns
Numbness, muscle weakness, or tingling, often in hands or feet
Inflammation of a brain region called the cerebellum

Background

Improper development of the white matter in the brain (leukodystrophy) in children with PBD-ZSD results in nerve damage, potentially affecting their development.
Damage to the nerves that send information from the brain to the rest of the body (peripheral neuropathy) can often cause numbness or weakness in the hands and/or feet.
Walking abnormality is the main neurological complication in adults with PBD-ZSD.
In people with mild forms of PBD-ZSD, nerve damage to the muscles, skin, and internal organs usually begins during adolescence.

You are your child’s Champion—learn how to best manage their condition

There is a high risk of liver involvement in progressing PBD-ZSD.

Signs and symptoms of liver damage

Patients with affected livers may exhibit some of the following symptoms:

Yellowing of skin and eyes (jaundice)
Pale, foul-smelling stools
Dark urine
Poor growth or low weight
Malnutrition, caused by an inability to absorb the fat-soluble vitamins A, D, E, and K
Inflammation of the liver
Enlarged liver (hepatomegaly)
Scarring of the liver (fibrosis and cirrhosis)

About the liver

The largest solid organ in the body, the liver performs more than 500 vital functions. Along with hundreds of other functions, the liver produces bile to digest the fats in food and cleans our blood by ridding our bodies of toxic substances.

How PBD-ZSD affects the liver

Liver cells in PBD-ZSD patients either completely lack or have a reduced number of functional peroxisomes, an important component of cells.
Peroxisomes in the liver are responsible for producing bile acids, which help remove toxins from the liver and absorb fats and vitamins in food.
When peroxisomes are absent or don’t work properly, they create harmful, or atypical, bile acids, which cannot do their job, and – along with toxins and waste materials – get trapped in the liver.
This toxic buildup can lead to serious liver damage.

If your child is diagnosed with PBD-ZSD, ask your doctor for a free liver test

The kidneys may be affected by PBD-ZSD

Signs and symptoms

Kidney stones
Kidney cysts (abnormal sacs)
Kidney failure

Background

Kidney problems are more common in children 4 years of age and older.
Older patients with PBD-ZSD should be monitored for hyperoxaluria, a condition of the kidneys that may lead to recurring bladder and kidney stones.
Kidney failure may also result in older patients and should be monitored.
Infants with PBD-ZSD may have abnormally large kidneys.

You are your child’s Champion—learn how to best manage their condition

People with PBD-ZSD may have low levels of certain hormones

Signs and symptoms

Muscle pain
Joint pain
Vomiting
Low levels of sodium
Low blood pressure
Darkening of your skin (hyperpigmentation)

Background

Poor function in the adrenal glands, small organs that produce hormones, is common and may be underdiagnosed in people with PBD-ZSD.
Hormone imbalances are fairly common in people with PBD-ZSD but may be overlooked.
Hormone imbalances do not always cause symptoms, highlighting the importance of screenings at routine doctor follow-ups.

You are your child’s Champion—learn how to best manage their condition

People with PBD-ZSD may have bone abnormalities

Signs and symptoms

Unusual spots on the ends of bones (ie, ankles, fingers)
Low bone density

Background

X-rays may show abnormal spots around the growth plates (the growing tissue near the ends of long bones in children and adolescents) in severe cases. Your doctor may call this condition “chondrodysplasia punctata.”
Decreased bone density has been linked to worsening of disease.
Fractures can occur at random. A dual-energy x-ray absorptiometry scan is a bone density scan that can assess bone strength and risk of a fracture.

You are your child’s Champion—learn how to best manage their condition

PBD-ZSD often affects the teeth

Signs and symptoms

Enamel abnormalities
Teeth slow to emerge
Small, poorly formed teeth
Orange-/yellow-colored teeth

Background

Dental examinations are recommended every 6 months.
Management of abnormalities in children’s permanent teeth depends on the severity of the problem.

You are your child’s Champion—learn how to best manage their condition

The ability to control movement is often affected by PBD-ZSD

Signs and symptoms

Poor movement
Walking abnormality
Low muscle tone and strength

Background

Delays in meeting developmental milestones, such as lacking head control or responding to sights or sounds.

You are your child’s Champion—learn how to best manage their condition

Being resourceful means having the right tools when you need them

No matter where your child is in her/his Zellweger spectrum disorder (ZSD) journey, there's going to be something more you need to know and do. Having the right resources can help you handle it.

Below are printable resources to help you initiate the conversations you need to have.

Effets on body

Learn more about the liver

Learn more detailed information about the liver and the role it plays in your child’s PBD-ZSD.

Effets on body

Does your child have a damaged liver?

This atypical bile acid test is an important way to see if your child’s liver is healthy. Ask your doctor to order this free test.

Uncover the underlying
cause of PBD-ZSD

PBD-ZSD can be confusing and overwhelming, but having all the facts can empower you to best support your child or loved one.

Click through the slideshow below to learn how PBD-ZSD develops and what you can expect when caring for a child with this disease.

Illustration of a human cell with a focus on the peroxisome. The loss of peroxisome function causes Zellweger spectrum disorders.

Illustration displaying normal peroxisome function.

PBD-ZSD is a set of genetic diseases caused by a loss of peroxisome function. Peroxisomes are important parts of your cells that are responsible for breaking down fats and chemicals, and getting rid of waste so that your body can function properly.

A family of genes called PEX provides the instructions for how to correctly assemble peroxisomes, Peroxisomes that are not assembled correctly will not function properly.

In people with PBD-ZSD, a permanent alteration in the PEX gene family leads to a loss of peroxisome function. If peroxisomes are not working, cells can no longer maintain their normal functions, altering the body’s usual routine and leading to many problems over time.

Because peroxisomes are present in almost all cells, loss of peroxisome function can cause harmful consequences to the entire body. Many key organs, including the brain, eyes, and liver, cannot function properly.

Let’s look at an example of how the absence of working peroxisomes can affect how an organ works. A large number of peroxisomes can be found in the liver, aiding in the production of bile and bile acids. Bile acids help to absorb fats and vitamins from the food you eat while eliminating cholesterol, waste, and other toxins from your body.

Because of the reduction or absence of working peroxisomes in the liver, bile acids cannot be made correctly. Toxic components, such as atypical bile acids and waste, get trapped in the liver, resulting in a condition called cholestasis. This toxic buildup can lead to inflammation, liver damage, and cirrhosis, which is when the liver becomes scarred and unable to function properly.

Peroxisomes play a similar role in different organ systems, so their abnormal function can lead to a variety of symptoms. People with PBD-ZSD may experience multisystemic complications including neurological problems and seizures, delayed growth and development, hearing and vision loss, poor muscle tone, and skeletal and dental abnormalities.

There is no way to predict exactly where a person's disease will fall on the spectrum. There are many factors that contribute to how the disease will affect someone, including the age at which their symptoms first start to appear, the number of functioning peroxisomes they have, and the rate at which the disease progresses.

Because it can affect many organ systems of the body, PBD-ZSD requires a diverse team of specialists to help monitor and manage the symptoms of disease. Talk to your healthcare team about routine checkups and the best ways to support your child or loved one with PBD-ZSD.

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