Niemann-Pick disease

Overview

Niemann-Pick disease is a group of rare conditions passed down in families. The conditions affect the body's ability to break down and use fats, such as cholesterol and lipids, inside cells. Because of the buildup of fats, these cells don't work as they should and, over time, the cells die. Niemann-Pick disease can affect the brain, nerves, liver, spleen and bone marrow. Sometimes it can affect the lungs.

Symptoms of Niemann-Pick disease relate to worsening function of the nerves, brain and other organs over time.

Niemann-Pick disease can happen at different ages but mainly affects children. The condition has no known cure and is sometimes fatal. Treatment is focused on helping people live with their symptoms.

Symptoms

The three main types of Niemann-Pick disease are called A, B and C. Symptoms differ widely but depend in part on the type and how severe the condition is. Symptoms may include:

• Loss of muscle control, such as clumsiness and problems walking.
• Muscle weakness and floppiness.
• Stiff and awkward movements.
• Vision problems, such as vision loss and eye movements that can't be controlled.
• Hearing loss.
• Being sensitive to touch.
• Problems sleeping.
• Problems swallowing and eating.
• Slurred speech.
• Problems with learning and memory that get worse.
• Mental health conditions, such as depression, paranoia and behavior problems.
• Liver and spleen that get too large.
• Repeated infections that cause pneumonia.

Some infants with type A show symptoms within the first few months of life. Those with type B may not show symptoms for years and have a better chance of living to adulthood. People with type C can start to have symptoms at any age but may not have any symptoms until adulthood.

When to see a doctor

If you have concerns about your child's growth and development, talk with your healthcare professional. If your child is no longer able to do some activities that could be done before, see your healthcare professional right away.

Causes

Niemann-Pick disease is caused by changes in specific genes related to how the body breaks down and uses fats. These fats include cholesterol and lipids. The gene changes are passed from parents to children in a pattern called autosomal recessive inheritance. This means that both the mother and the father must pass on a changed gene for the child to have the condition.

Categories of Niemann-Pick disease

There are three types of Niemann-Pick disease: A, B and C.

Types A and B

Niemann-Pick disease types A and B are both caused by changes in the SMPD1 gene. The condition is sometimes called acid sphingomyelinase deficiency (ASMD). With these gene changes, an enzyme called sphingomyelinase (sfing-go-MY-uh-lin-ase) is missing or doesn't work well. This enzyme is needed to break down and use lipids called sphingomyelin inside cells. A buildup of these fats causes cell damage, and over time, the cells die.

Type A ― the most severe form ― begins in infancy. Symptoms include a liver that becomes too large, severe brain damage and nerve loss that worsens over time. There is no cure. Most children do not live past a few years of age.

Type B ― sometimes called juvenile-onset Niemann-Pick disease ― usually begins later in childhood. It does not involve damage to the brain. Symptoms include nerve pain, problems walking, vision problems, and a liver and spleen that become too large. Lung problems also can happen. Most people with type B live into adulthood. But liver and lung problems worsen over time. Some people have symptoms that overlap between types A and B.

Type C

Niemann-Pick disease type C is caused by changes in the NPC1 and NPC2 genes. With these changes, the body doesn't have the proteins it needs to move and use cholesterol and other lipids in cells. Cholesterol and other lipids build up in the cells of the liver, spleen or lungs. Over time, the nerves and brain also are affected. This causes problems with eye movements, walking, swallowing, hearing and thinking. Symptoms vary widely, can appear at any age and get worse over time.

Risk factors

Risk factors for Niemann-Pick disease depend on the type. The condition is caused by changes in genes that are passed down in families. Although the condition can occur in any population, type A occurs more often in people of Ashkenazi Jewish descent. Type B occurs more often in people of North African descent. Type C occurs in many different populations, but it occurs more often in people of Acadian and Bedouin descent.

If you have a child with Niemann-Pick disease, your risk of having another child with the condition is higher.

Genetic testing and counseling can help you learn about your risks.