What are the other Names for this Condition? (Also known as/Synonyms)

• Niemann Pick Disease, Type B

What is Niemann-Pick Disease Type B? (Definition/Background Information)

• Niemann-Pick Disease Type B is an inherited condition involving lipid metabolism. People with this condition experience a build up of lipids in the spleen, liver, lungs, bone marrow, and brain
• Signs and symptoms typically develop in the pre-teen years and may include enlarged liver and spleen (hepatosplenomegaly), short stature, problems with lung function including frequent lung infections, and a low number of platelets in the blood (thrombocytopenia)
• Niemann-Pick Disease Type B is caused by changes (mutations or variants) in the SMPD1 gene. It is inherited in an autosomal recessive fashion
• Treatment is aimed at addressing the symptoms present in each individual. Bone marrow transplantation has been attempted in a few individuals. Researchers are working to develop additional options for treatment, including enzyme replacement and gene therapy

(Source: Niemann-Pick Disease Type B; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

Who gets Niemann-Pick Disease Type B? (Age and Sex Distribution)

• Niemann-Pick Disease Type B is a rare, congenital disorder. The presentation of symptoms typically occurs in childhood
• Both males and females may be affected
• Worldwide, individuals of all racial and ethnic groups may be affected

What are the Risk Factors for Niemann-Pick Disease Type B? (Predisposing Factors)

• A positive family history may be an important risk factor, since Niemann-Pick Disease Type B is an inherited condition
• Currently, no other risk factors have been clearly identified for the disorder

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Niemann-Pick Disease Type B? (Etiology)

Niemann-Pick Disease Type B is caused by mutation(s) in the SMPD1 gene.

• This gene codes for an enzyme known as sphingomyelinase, found in the cellular recycling centers known as lysosomes
• In Niemann-Pick Disease Type B, the mutation(s) in the gene allow some activity of the enzyme
• The condition is inherited in an autosomal recessive manner

Autosomal recessive: Autosomal recessive conditions are traits or disorders that occur when two copies of an abnormal gene have been inherited on a non-sex chromosome. If both parents have an autosomal recessive condition, there is a 100% likelihood of passing on the mutated genes to their children. If, however, only one mutant copy of the gene is inherited, the individual will be a carrier of the condition, but will not be present with any symptoms. Children born to two carriers, have a 25% chance of being homozygous dominant (unaffected), a 50% chance of being heterozygous (carrier), and a 25% chance of being homozygous recessive (affected).

What are the Signs and Symptoms of Niemann-Pick Disease Type B?

The signs and symptoms of Niemann-Pick Disease Type B may include:

• Abnormal macular morphology 
• Bone-marrow foam cells 
• Decreased circulating high-density lipoprotein levels
• Diffuse reticular or finely nodular infiltrations 
• Dyspnea 
• Foam cells with lamellar inclusion bodies 
• Hepatomegaly
• Hypertriglyceridemia
• Increased circulating low-density lipoprotein levels
• Recurrent respiratory infections
• Sea-blue histiocytosis 
• Short stature
• Splenomegaly

(Source: Niemann-Pick Disease Type B; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

How is Niemann-Pick Disease Type B Diagnosed?

Niemann-Pick Disease Type B is diagnosed on the basis of the following information:

• Complete physical examination
• Thorough medical history evaluation
• Assessment of signs and symptoms
• Laboratory tests
• Imaging studies
• Biopsy studies, if necessary
• Molecular genetic testing of:
• Members of an affected family to check one is a carrier of a causative gene mutation
• Developing fetal cells, if there is a family history of the disorder

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Niemann-Pick Disease Type B?

The complications of Niemann-Pick Disease Type B may include:

• Compromised function of the liver and spleen
• Heart disease

Complications may occur with or without treatment, and in some cases, due to treatment also.

How is Niemann-Pick Disease Type B Treated?

There is no cure for Niemann-Pick Disease Type B, since it is a genetic condition. The treatment is usually given to manage the signs and symptoms and any complication that develops.

How can Niemann-Pick Disease Type B be Prevented?

Currently, Niemann-Pick Disease Type B may not be preventable, since it is a genetic disorder.

• If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders

Regular medical screening at periodic intervals with tests and physical examinations are recommended.

What is the Prognosis of Niemann-Pick Disease Type B? (Outcomes/Resolutions)

• The prognosis of Niemann-Pick Disease Type B is dependent upon the severity of the signs and symptoms and associated complications, if any
• It has been reported that individuals affected by Niemann-Pick Disease Type B often survive till adulthood. Although, there is involvement of the lungs, liver and spleen in this subtype, the affected individuals typically do not develop neurological symptoms
• Typically, the prognosis may be assessed on a case-by-case basis

Additional and Relevant Useful Information for Niemann-Pick Disease Type B:

The following DoveMed website link is a useful resource for additional information:

http://www.dovemed.com/diseases-conditions/rare-disorders/