What is Niemann-Pick Disease?

This disorder (Niemann-Pick disease) refers to a group of inherited metabolic disorders known as the leukodystrophies or lipid storage diseases in which harmful quantities of a fatty substance (lipids) accumulate in the liver, spleen, bone marrow, lungs, and the brain.

There are four main types of Niemann-Pick disease:
• Type A – Patients with this type have severe brain damage and usually die by age two or three.
• Type B – Affects the liver and spleen. Organs enlarge during the pre-teen years. There is usually no brain damage. Patients usually suffer from breathing problems and die in teen years.
• Type C – Produces extensive brain damage. The liver and spleen are moderately enlarged. Usually starts in childhood and leads to death in teen years.
• Type D – This is similar to type C, but occurs only in people related to a family that lived in Nova Scotia at the start of the 1700s.

Causes of Niemann-Pick Disease:

Niemann-Pick disease is an autosomal recessive trait, which means that both parents must carry the abnormal gene for their child to inherit the disorder.

The exact cause depends on the type of Niemann-Pick disease:

Types A and B - A fatty material called sphingomyelin builds up in the patient's organs. This substance is normally present in the membrane of most cells. The enzyme acid sphingomyelinase normally breaks down this substance. However, people with type A or B either do not have enough of this enzyme or this enzyme does not work properly. Without the properly functioning enzyme, this fatty material builds up in the cells. The cells die and the organ does not work properly.

Types C and D – In these types of Niemann-Pick Disease, nerve cells in the brain are unable to move cholesterol out. This allows cholesterol to build up, which keeps cells from functioning properly.

Symptoms of Niemann-Pick Disease:

Symptoms of Niemann-Pick may develop during childhood or the teen years, depending on the type of the disease. Not all patients will develop every symptom. Symptoms may include:

Type A – In this type of Niemann-Pick symptoms begin within the first few months of life. They may include yellow skin and eye coloration, enlarged belly (due to enlarged liver and spleen), mental retardation, failure to thrive, difficulty swallowing and feeding, seizures, visual problems, rigid muscles, and spastic movements etc.

Type B - Symptoms start during pre-teen years. They may include yellow skin and eye coloration, enlarged belly (due to enlarged liver and spleen), enlarged lymph nodes, Osteoporosis or brittle bones, breathing difficulties and frequent respiratory infections etc.

Type C and D - In these types of Niemann-Pick disease, symptoms may start in childhood or teen years. They may include yellow skin and eye coloration, trouble walking, difficulty swallowing, unable to look up or down, enlarged spleen and liver, learning problems, sudden loss of muscle tone, seizures etc.

Diagnosis of Niemann-Pick Disease:

For diagnosing of this disorder doctors will ask about the patient’s symptoms and medical history, and perform a physical exam and following tests may include –
For all types –
1. Complete blood cell count (CBC), measurement of acid sphingomylinase activity in white blood cells.
2. DNA testing – to look for a mutated gene associated with the disease.
For type C –
Skin biopsy – removal of a skin sample to check how it transports and stores cholesterol

Treatment of Niemann-Pick Disease:

There is no specific treatment currently for this disorder. Bone marrow transplantation has been attempted in a few cases of type B, Eenzyme replacement and gene therapies might also be helpful for those with type B. Individuals with types C and D are normally placed on a low-cholesterol diet.