Niemann-Pick disease type C

Overview

Niemann-Pick disease type C (often shortened to NPC) is a very rare, inherited disease that causes damage to the nervous system over time. It results from an abnormal processing in body tissues of fatty substances (called lipids), particularly cholesterol.

With the body being unable to properly break down these fats, an abnormally large cholesterol buildup develops in the spleen and liver, while harmful amounts of other lipids begin to collect in the brain.

As a result of the damaging accumulation of lipids throughout the body, NPC may affect the physical, neurological, emotional and cognitive functioning of people with this rare disease.

Symptoms

Symptoms may begin at any age, most commonly in school age children. However, infants, adolescents and adults can all be affected by the disease.

With greater awareness and better diagnostic methods, more patients are being identified in adulthood. Progression is more rapid with earlier onset.

Childhood symptoms

Childhood symptoms of NPC may be first noticed when a child starts going to school and concerns regarding their behaviour are raised. As the disease progresses, children may experience developmental delays, challenges with motor skills (e.g. increased clumsiness and abnormal posturing) and a particular difficulty in making vertical eye movements.

"Falling with laughter"

Another particular symptom is episodes of falling with laughter – called “gelastic cataplexy”. This is due to a sudden loss of muscle tone.

Dementia-related symptoms

People who begin to show signs of NPC in their early adulthood are more likely to develop symptoms of dementia than those people who develop NPC at a younger age. The dementia-related symptoms are characterized by initial impairments in executive functions such as:

• Disinhibition,
• Inflexibility of thinking,
• Poor judgement,
• Lack of insight,
• Inability to understand abstract concepts,
• Poor attention, and
• Mental slowing.

These symptoms can be followed by increasing difficulty with short-term memory and learning.

Other symptoms

Other symptoms of NPC may include:

• An enlarged liver or spleen,
• Challenges with swallowing,
• Slurred speech,
• Loss of muscle strength,
• Seizures,
• Breathing problems, and
• Gradual liver failure.

Diagnosis

If a person has the clinical features of NPC, neurologists or specialists in genetic diseases may perform a skin biopsy. This procedure requires the removal of a small piece of skin that is sent to a special laboratory where cells are cultured and then tested for the capacity to process cholesterol.

DNA testing may also be recommended to look for mutations in one of two genes (NPC1 and NPC2) that could be causing abnormal function of proteins involved in processing of cholesterol and other fatty substances (lipids).

A new diagnostic test that requires blood measures the products of cholesterol processing.

Risk factors

NPC is an inherited disease caused by the body’s inability to properly metabolize (break down) cholesterol and lipids. This lack of ability to process cholesterol in the body is the result of a genetic mutation in either the NPC1 or NPC2 gene.

Treatment

There is currently no cure for NPC. However, there is now a drug called Miglustat that can prevent the body from producing excess lipids to delay progression of the disease. As a result, early diagnosis has become important.

Other medications

Other medications can help manage some of the symptoms caused by NPC, such as seizures, but they cannot stop the progression of the disease.

Research on potential treatments has been moving forward since 1997, when scientists identified the NPC1 gene involved in NPC.

Therapeutic approaches

Therapeutic approaches also support people living with NPC to manage symptoms of their disease:

• Occupational and physical therapies may help improve the functional ability of people living with NPC through exercises that are focused on movement and improving muscle strength.
• Speech therapy can help improve verbal communication and can also address any swallowing issues that may result from the progression of NPC.