What is Niemann-Pick Disease?
Niemann-Pick is an inherited disease that affects lipid metabolism, or the way fats, lipids, and cholesterol are stored in or removed from the body. In people with Niemann-Pick, abnormal lipid metabolism causes the buildup of harmful amounts of lipids in various organs. The disease primarily affects the liver, spleen, bone marrow, and brain.
The disease is broken down into five types—type A, type B, type C, type D, and type E.
Types A and B are referred to as type I. Types C and D are referred to as type II. The term “Type D” is no longer in use—research found that those formerly though to have Type D actually have a variant of Type C (Genetics Home Reference, 2012). Type E is a less-common, adult-onset version of Niemann-Pick disease.
Organs affected, symptoms, and treatments vary based on the particular type of Niemann-Pick disease. However, every type of the disease is extremely severe, and can seriously shorten a person’s life expectancy.
What Causes Niemann-Pick Disease?
Types A and B
Types A and B occur when acid sphingomyelinase (ASM) is not properly produced in the body, specifically in the white blood cells. ASM is an enzyme that helps remove fats in all the cells of the body.
Sphingomyelin, the fats that ASM remove, can build up in the cells when ASM is not properly breaking it down. When sphingomyelin builds up, cells begin to die and organs stop functioning correctly.
Type C is primarily concerned with the body’s inability to efficiently remove excess cholesterol and other lipids. Without proper breakdown, cholesterol builds up in the spleen and liver, and excessive amounts of other fats accumulate in the brain.
Type D occurs when the body cannot properly move cholesterol between cells of the brain, and is believed to be a variant of type C (NLM).
Type E is a rare type of Niemann-Pick disease that occurs in adults. Little is known about this type.
Symptoms of Niemann-Pick Disease
Symptoms of type A of Niemann-Pick disease are present within the first few months of a child’s life and include:
- swelling of the abdomen (usually around 3 to 6 months of age) from enlargement of the liver and spleen
- swollen lymph nodes
- a red spot inside the eye
- difficulty feeding
- difficulty with basic motor skills, poor muscle tone
- brain damage
- lung disease
- frequent respiratory infections
Symptoms of type B of Niemann-Pick disease usual begin to appear in late childhood or adolescence. Type B does not include the motor difficulty commonly found in type A. Symptoms of type B may include:
- swelling of the abdomen (often begins in early childhood) from enlargement of the liver and spleen
- respiratory infections
- poor coordination, mental retardation, psychiatric disorders
- delayed growth, or failure to develop at a normal rate, causing short stature
Types C and D
Symptoms of type C of Niemann-Pick disease usually begin to appear in children around 5 years old. However, type C could appear anytime in a person’s life, from birth to adulthood. Symptoms of types C and D include any of the following:
- difficulty moving limbs
- enlarged spleen and/or liver
- yellowing of the skin after birth (jaundice)
- difficulty learning
- decline of intellect (dementia)
- difficulty speaking
- loss of muscular functioning
- difficulty moving the eyes (especially in an up-and-down direction)
- unsteadiness, difficulty walking, or clumsiness
- loss of vision or hearing
- brain damage
Symptoms of type E of Niemann-Pick disease are present in adults. This type is quite rare and research on the condition is limited, but the symptoms include:
- swelling of the spleen
- swelling of the brain
- neurological problems (swelling within the nervous system)
Diagnosing Niemann-Pick Disease
Types A and B
To diagnose types A and B of Niemann-Pick disease, a doctor will test the blood or bone marrow to measure the amount of ASM in white blood cells. This type of testing can determine whether a person has Niemann-Pick disease; DNA testing can also determine if you are a carrier of the disease.
Type C and D
Types C and D are usually diagnosed by a skin biopsy. Once a sample is taken, laboratory scientists will analyze how the skin cells grow, as well as how they move and store cholesterol. A doctor may also use DNA testing to look for the genes that cause type C.
Treating Niemann-Pick Disease
There is no known treatment for type A at this time.
Several treatment options, including bone marrow transplants, enzyme replacement therapy, and gene therapy have been used. Research is ongoing to determine the effectiveness of such treatments.
A medication called miglustat is currently used to treat type C. Miglustat is classified as an enzyme inhibitor, and works by preventing the body from producing fatty substances (in the case of type C, cholesterol) so that less of it will build up in the body.
There is no specific treatment for type D at this time.
Most children born with Niemann-Pick type A die in infancy; however, some live to the age of 4.
Those with Niemann-Pick type B may survive into late childhood or early adulthood, but often experience health problems such as respiratory failure, or complications related to an enlarged liver or spleen.
Type C and D
Niemann-Pick type C is always fatal; however, the outlook for this type depends on when symptoms begin. If symptoms appear in infancy, the child is not likely to live past 5 years old. If symptoms appear after 5 years of age, the child is likely to live to around 20 years old. Each person, depending on his or her symptoms and severity, may have a slightly different prognosis (NNPDF).