Niemann-Pick disease

Causes

Niemann-Pick disease types A and B occur when cells in the body do not have an enzyme called acid sphingomyelinase (ASM). This substance helps break down (metabolize) a fatty substance called sphingomyelin, which is found in every cell in the body.

If ASM is missing or does not work properly, sphingomyelin builds up inside cells. This kills your cells and makes it hard for organs to work properly.

Type A occurs in all races and ethnicities. It is more common in the Ashkenazi (Eastern European) Jew population.

Type C occurs when the body cannot properly break down cholesterol and other fats (lipids). This leads to too much cholesterol in the liver and spleen and too much of other lipids in the brain. Type C is most common among Puerto Ricans of Spanish descent.

Type D involves a defect that interferes with how cholesterole moves between brain cells. It is a variant of type C. This type has only been seen in French Canadian people in Yarmouth County, Nova Scotia.

Symptoms

Symptoms vary. Other health conditions may cause similar symptoms. The early stages of the disease may only cause a few symptoms. You may never have all symptoms.

Type A usually begins in the first few months of life. Symptoms may include:

• Abdominal (belly area) swelling within 3 - 6 months
• Cherry red spot in the eye
• Feeding difficulties
• Loss of early motor skills (gets worse over time)

Type B symptoms are usually milder. They occur in late childhood or the teenage years. Abdominal swelling may occur in young children. There is almost no brain and nervous system involvement, such as loss of motor skills. Some patients may have repeated respiratory infections.

Type C usually affects school-aged children. However, it may occur any time between early infancy to adulthood. Symptoms may include:

• Difficulty moving limbs (dystonia)
• Enlarged spleen
• Enlarged liver
• Jaundice at (or shortly after) birth
• Learning difficulties and intellectual decline (dementia)
• Seizures
• Slurred, irregular speech
• Sudden loss of muscle tone which may lead to falls (cataplexy)
• Tremors
• Trouble moving the eyes up and down (vertical supranuclear gaze palsy)
• Unsteady gait, clumsiness, walking problems (ataxia)

Symptoms of Type D are similar to Type C.

Exams and Tests

A blood or bone marrow test can be done to diagnose types A and B. The test can tell who has the disease, but does not show if you are a carrier. DNA tests can be done to diagnose carriers of  types A and B.

A skin biopsy is usually done to diagnose types C and D. The health care provider watches how the skin cells grow, move, and store cholesterol. DNA tests may also be done to look for the two genes that cause this type

Other tests might include:

• Bone marrow aspiration
• Liver biopsy (usually not needed)
• Slit-lamp eye exam
• Sphingomyelinase assays

Treatment

At this time, there is no effective treatment for type A.

Bone marrow transplants have been done on a few patients with type B with encouraging results. Researchers continue to study possible treatments, including enzyme replacement and gene therapy.

There is no specific treatment for Type D. A new medicine called miglustat is available for the nervous system symptoms of type C.

A healthy, low-cholesterol diet is recommended. However, research does not show that these methods stop the disease from getting worse or change how cells break down cholesterol. However, medicines are available to control or relieve many symptoms, such as cataplexy and seizures.

Support Groups

For more information, visit the National Niemann-Pick Disease Foundation website: www.nnpdf.org

Outlook (Prognosis)

Type A Niemann-Pick is a severe disease. It usually leads to death by age 2 or 3.

Those with type B may live into late childhood or adulthood.

A child who shows signs of type C before age 1 may not live to school age. Those who show show symptoms after entering school may live into their mid-to-late teens. Some may live into their 20s.

Possible Complications

• Blindness
• Brain damage with intellectual disability and delayed development of physical skills
• Deafness
• Death

When to Contact a Medical Professional

Make an appointment with your health care provider if you have a family history of Niemann-Pick disease and you plan to have children. Genetic counseling and screening is recommended.

Call your health care provider if your child has symptoms of this disease, including:

• Developmental problems
• Feeding problems
• Poor weight gain

Prevention

All types of Niemann-Pick are autosomal recessive. This means that both parents are carriers -- they each carry one copy of the abnormal gene without having any signs of the disease themselves.

When both parents are carriers, there is a 25% chance that their child will have the disease and a 50% chance that a child will be a carrier.

Carrier detection testing is only possible if the genetic defect is identified. The defects involved in types A and B have been well-studied. DNA tests for these forms of Niemann-Pick are available.

Genetic defects have been identified in the DNA of many patients with type C. It may be possible to diagnose people who carry the abnormal gene.

A few centers offer tests to diagnose a baby still in the womb.

Alternative Names

Sphingomyelinase deficiency

References

Krasnewich DM, Sidransky E. The lysosomal storage diseases. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 215.

McGovern MM, Desnick RJ. Lipidoses (Lysosomal Storage Diseases). In: Kliegman RM, Stanton BF, St. Geme JW III, Schor NF, Behrman RE, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap80.4.

NP-C Guidelines Working Group, Wraith JE, Baumgartner MR, Bembi B, et al. Recommendations on the diagnosis and management of Niemann-Pick disease type C. Mol Genet Metab. 2009;98:152-165.

Update Date: 12/7/2012

Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang.