Niemann-Pick Disease Type B

Niemann-Pick disease is a rare genetic condition that affects many of the body’s organs and systems, including the central nervous system. It is one of about 50 diseases classified as lysosomal storage disorders (LSD), where a genetic variation disrupts the normal activity of lysosomes in human cells. Niemann-Pick disease type B, is a subtype of Niemann-Pick disease, classified according to the specific genetic cause of the disease and the symptoms of the disease.

Lysosomes contain specific proteins (enzymes) responsible for breaking down and recycling molecules such as fats and sugars. Individuals with a lysosomal storage disorder lack one of these necessary enzymes or do not have one of these enzymes in sufficient quantities to break down molecules for proper cell function.

Signs and symptoms of Niemann-Pick disease type B generally first present in school-aged children and become more pronounced as the child ages.

Symptoms may experience:

• Enlarged liver and spleen (hepatosplenomegaly)
• Short stature
• Frequent respiratory infections
• Lung disease/infection
• Low blood platelets (thrombocytopenia)
• Delayed bone age (slow mineralization of bone)
• Visual changes or difficulties (cherry-red spot)

Niemann-Pick disease type B is caused by a mutation in a gene known as SMPD1, which provides instructions for the production of an enzyme called acid sphingomyelinase. This enzyme is located in a cell’s lysosomes and is responsible for the conversion and recycling of a specific fat molecule. Genetic mutations in the SMPD1 gene result in a deficiency of acid sphingomyelinase, leading to an accumulation of fat molecules in cells which eventually causes cells to malfunction. This genetic condition is inherited in an autosomal recessive pattern, meaning that an affected child has received one defective copy of the SMPD1 gene from each of their parents.

There are currently no approved therapies to reverse the effects of Niemann-Pick disease. Current approaches to Niemann-Pick disease type B involve supportive therapies and targeted management for specific symptoms.

At the Boston Children’s Lysosomal Storage Disorders (BoLD) Program, our team of providers is committed to the care of complex patients. As part of Boston Children’s Hospital, we are prepared to meet the challenge of providing multifaceted care by partnering with you and your child to deliver direct care in our BoLD clinic. We work with the broad array of world-class specialists at Boston Children’s to optimize the care we provide your child with Niemann-Pick disease type B.