Niemann-Pick Disease

Group of storage disorders

Niemann-Pick disease refers to a group of inherited disorders known as leukodystrophies or lipid storage disorders in which certain fats accumulate in the tissues like the brain and liver and cause damage. In Niemann-Pick disease, the body is unable to break down fats completely, so they accumulate in the tissues and cause damage.

Certain groups have higher risk

Niemann-Pick disease affects all groups of people and both males and females. However, certain populations have a higher incidence of the disease:

• Ashkenazi Jewish population (Types A and B)
• French Canadian population of Nova Scotia (Type D)
• Maghreb region (Tunisia, Morocco, Algeria) of North Africa (Type B)
• Spanish-American population of southern New Mexico and Colorado (Type C)

The four types of Niemann-Pick disease are commonly called Type A, Type B, Type C, and Type D. Sometimes Type A and B are grouped together as Type I and C and D are grouped together as Type II.

Niemann-Pick Type A

• Caused by deficiency of the enzyme acid sphingomyelinase (ASM) which is needed to break down a type of fat called sphingomyelin.
• In Type A, there is usually less than 1% of the normal level present in the body
• This leads to accumulation of a fat (sphingomyelin) which damages cells
• Causes severe nervous system disease
• Usually leads to death usually by 18 months to 2 years of age
• Most cases (85%) of Neimann-Pick are Type A

Niemann-Pick Type B

• Like Type A is caused by deficiency of acid sphingomyelinase (ASM), but less servere
• In Type B, there is usually about 10% of the normal level is present in the body
• Leads to accumulation of sphingomyelin which damages cells
• Little or no neurological problems
• Longer life expectancy than the other types--into adulthood

Neimann-Pick Types C and D

• Caused by inability to break down or transport cholesterol
• Leads to accumulation of cholesterol and other fats in the liver, spleen, and brain
• Nervous system disease develops
• Leads to death usually by age 20
• Most rare type of Niemann-Pick (possibly 500 cases worldwide)

Symptoms

One of the difficulties in correctly diagnosing Niemann-Pick disease is that its symptoms can be different in each person affected. Types A and C may have symptoms such as:

• enlarged liver
• brain damage
• difficulty walking and swallowing
• increased sensitivity to touch
• difficulty speaking
• loss of muscle tone (hypotonia)
• learning difficulties

Type B does not have the nervous system symptoms. People with Type B often have repeated respiratory infections and an enlarged liver and spleen.

Diagnosis

Types A and B can be diagnosed by measuring the ASM activity in white blood cells. Low levels would point to Niemann-Pick disease. Type C can be diagnosed by examining a skin sample (biopsy) for cholesterol storage.

Treatment

As yet, there are no specific treatments for any of the types of Niemann-Pick disease. Bone marrow transplant has been attempted in several individuals with Type B. People with Types C and D are often placed on a low-cholesterol diet. Supportive care through nutrition, medication, physical therapy, and being followed by specialists can help with quality of life.

_Sources:

"NINDS Niemann-Pick Disease Information Page." Disorders A - Z. 18 June 2007. National Institute of Neurological Disorders and Stroke. 20 Feb 2009.

"Disease Overview." Niemann-Pick Disease. National Niemann-Pick Disease Foundation. 20 Feb 2009.