What Is Niemann-Pick Disease Type C1?
Niemann-Pick disease type C (NPC) is an inherited condition in which the body cannot properly metabolize cholesterol and fats, resulting in an excess of these substances in the body. Cholesterol buildup in the liver causes severe liver disease, and fat accumulation in the brain leads to learning disabilities and progressive neurological symptoms.
Niemann-Pick disease type C can be caused by mutations in two different genes. Type C1 is caused by mutations in the NPC1 gene, and type C2 is caused by mutations in the NPC2 gene. Although the genes are different, the resulting symptoms are the same because NPC1 and NPC2 must work together to remove cholesterol and lipids from body cells. Of the known cases of Niemann-Pick disease type C, 95% have been type C1 and 5% have been C2.
The first symptoms of the disease, which can appear at any age from infancy to adulthood, are an enlarged liver, an enlarged spleen, and/or jaundice. In some cases, it is possible to detect the disease in an unborn child via ultrasound, but the disease is most commonly diagnosed in school-aged children. Symptoms may include sudden muscle problems such as seizures, clumsiness, tremors, problems walking, sudden falls, slurred speech, and trouble moving the eyes up and down. As the condition progresses, these children develop learning disabilities, psychological problems, or even dementia, and often lose the ability to speak. Eventually, individuals with Niemann-Pick disease type C lose the ability to move their facial muscles or swallow, making feeding through a stomach tube necessary.
For those diagnosed during childhood, the disease is usually fatal in the late teens or twenties due to pneumonia. Those diagnosed in adulthood generally survive 10 to 20 years after diagnosis.
How Common Is Niemann-Pick Disease Type C?
It is estimated that Niemann-Pick disease type C affects 1 in 150,000 individuals, with approximately 95% of these cases being attributed to NPC1. It is more common among French Acadians in Nova Scotia, people of Hispanic descent in specific parts of Colorado and New Mexico, and a small Bedouin group in Israel.
How Is Niemann-Pick Disease Type C Treated?
At this time, there is no cure for Niemann-Pick disease type C. Treatment focuses on managing symptoms with medication for seizures, sedatives for sleep disturbances, physical therapy to maintain mobility, and speech therapy to preserve communication as long as possible. Chest physiotherapy and antibiotics may help to prevent regular lung infections. Individuals with the condition need a gastronomy tube for feeding when they can no longer swallow well enough to avoid choking or malnutrition.
What Is the Prognosis for an Individual with Niemann-Pick Disease Type C?
For Niemann-Pick disease type C, an earlier age of onset is associated with a faster disease progression, while later onset is associated with slower progression and more attenuated symptoms. Individuals diagnosed in infancy rarely survive beyond 5 years. For those diagnosed during childhood, the disease is usually fatal in the late teens or twenties due to pneumonia. Those diagnosed in adulthood generally survive 10 to 20 years or more after diagnosis. Individuals presenting in adulthood are also more likely to have isolated psychiatric signs for years before developing more classic symptoms. The majority of individuals with Niemann-Pick disease type C develop symptoms in childhood.