Niemann-Pick disease

Niemann-Pick disease0

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.

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.

Diagnosis

Diagnosis of Niemann-Pick disease begins with a physical exam. The exam may show an early warning sign such as a liver or spleen that is too large. Your healthcare professional talks with you about symptoms and your family health history. Niemann-Pick disease is rare, and its symptoms can be similar to those of other health conditions, so testing is needed to get the right diagnosis.

Diagnostic tests depend on the type of Niemann-Pick disease.

Type A or B. Using blood or a tiny sample of skin, experts measure how much sphingomyelinase is in white blood cells. Sphingomyelinase is an enzyme that breaks down and uses fat.

Type C. Experts use a blood sample to measure levels of a specific type of cholesterol called oxysterol. In rare cases, a small sample of skin also can be used to tell how the cells move and store cholesterol.

Other tests also may be done, such as:

Genetic testing. DNA testing of a blood sample may show the specific gene changes that cause Niemann-Pick disease types A, B and C. People who have only one copy of the gene change but do not have the condition are called carriers. DNA tests can show carriers for all types of Niemann-Pick disease if the gene changes have been identified in the first person in a family to have the condition. The gene change can be passed on to children.

Magnetic resonance imaging (MRI). An MRI of the brain may show loss of brain cells. But in the early stages of Niemann-Pick disease, an MRI may not show any changes because symptoms usually show up before the loss of brain cells. MRI also can be used to look at the liver and spleen to see if they are large and to measure their size.

Eye exam. An eye exam may show changes that could be caused by Niemann-Pick disease, such as problems with eye movements in type C and changes inside the eyes in types A and B.

Prenatal testing. Ultrasound during pregnancy can show the large liver and spleen caused by Niemann-Pick disease type C. The liver and spleen also may be large in type A, but rarely in type B. Taking a sample of amniotic fluid from around the baby in the womb or taking a sample of tissue from the placenta may be done to diagnose Niemann-Pick disease.

Genetic testing and counseling for families with a child with Niemann-Pick disease can give information about risks and family planning options.

Treatment

No cure exists for Niemann-Pick disease, but supportive care can help manage symptoms.

Medicines

For Niemann-Pick disease type B, olipudase alfa-rpcp (Xenpozyme) is an enzyme replacement for missing or low levels of the sphingomyelinase enzyme. This enzyme replacement may help with lung problems and breathing and lessen the size of the liver and spleen. The medicine also may help height growth in children. It does not help with nerve-related symptoms.

Olipudase alfa-rpcp is given through a vein every two weeks.

For people with Niemann-Pick disease type C who have mild to moderate nerve symptoms, a drug called miglustat may be an option. Miglustat is approved for neurological symptoms of Niemann-Pick disease type C in many countries but is not approved by the U.S. Food and Drug Administration for this use in the United States.

Miglustat is a pill that's taken 1 to 3 times a day. Miglustat may slow the worsening of nerve symptoms such as problems with hearing, swallowing and walking. It also may help slow changes in mental health and learning and memory.

Discuss medicines, including possible side effects, with your doctor or other healthcare professional.

Supportive therapies

Therapies for all types of Niemann-Pick disease depend on symptoms and may include:

Speech, physical and occupational therapy. Physical therapy and occupational therapy can help keep the ability to move as long as possible. Speech therapy may help with talking and swallowing.

Nutrition therapy. This includes special foods that can be added to the diet when swallowing becomes difficult.

Oxygen therapy. This can help if the lungs are affected and problems with breathing happen.

Treatment of symptoms. Treatments can help with infections, seizures, muscle movements that can't be controlled and sleep problems.

People with Niemann-Pick disease need to see their healthcare professionals regularly, because the disease and its symptoms worsen over time. Research for new treatments is ongoing.

Type of Doctor Department : Neurologists, geneticists