This information comes from Alzheimer’s Society, a wonderful organization based out of the UK. They are one of my go-to sources for information and I highly recommend taking a look around their website. They offer the information on their website to be freely used by others, so I am posting the information in full. You can access the same article on their website as well as resources on dementia by clicking on the title, below.
But first, a little bit from the University of Notre Dame:
The National Institutes of Health refers to Niemann-Pick disease type C as “childhood Alzheimer’s” because of similarities in the brains of NPC and Alzheimer’s disease patients. Symptoms can include deterioration of memory and balance, lung and liver failure, delayed motor development, and seizures. The disease usually appears in early childhood, leading to neurological problems that are typically fatal.
From the Addi & Cassi Fund webpage (the twins with NPC pictured, above):
Every person in the world is born with the Niemann Pick Type C gene and could not live without it. The NPC1 gene is located on Chromosome 18 and the gene regulates human cholesterol metabolism at the cellular level. We were born with major problems on this cholesterol gene which in turn causes our fatal disease.
Some doctors believe Niemann Pick Type C and Alzheimer’s could be connected due to cholesterol and lipid issues (see The Scientist Magazine article, November 2008) while virus researchers have discovered that the Niemann Pick Type C gene helps both HIV-AIDS and Ebola infect humans. We are told by top scientists that because our cholesterol gene does not work, we can’t get infected with many viruses that infect people who have healthy functioning NPC genes.
According to Dr. Francis S. Collins, Director of the NIH, “While many of the genes we will initially be pursuing are responsible for rare disorders, what we learn from rare disorders often has profound consequences for our understanding of more common conditions.”
When I was writing my thesis on technologies for dementia, the youngest case of dementia that I found recorded was in a 6 year old girl who had Niemann-Pick disease type C – you can read about it in this article from Alzheimer Society, starting on page 16. You can also read one of my other posts about a 12-year old girl with this disorder here (og på dansk her).
How are Niemann-Pick disease type C and dementia related?
Niemann-Pick disease type C is one of a group of rare inherited disorders. It is not related to frontotemporal dementia, which is also sometimes called Pick’s disease. It mainly affects school-age children but can occur at any time, from early infancy to adulthood. It is caused by an inherited inability to deal with cholesterol and other fats, causing them to accumulate in cells, including those in the brain. This can lead to progressive loss of movement and difficulties with walking and swallowing.
People who first show symptoms in late adolescence or early adulthood are more likely to experience dementia as part of the disease. The dementia symptoms include confusion, memory problems and difficulties in concentrating and learning.
There is currently no treatment for the disease, and life expectancy varies. However, researchers have identified the responsible gene and there is continuing research into this area. For further information and support contact the Niemann-Pick Disease Group (see ‘Other useful organisations’).
© Copyright 1998-2015 Alzheimer’s Society. All rights reserved.
And some more information from the National Niemann-Pick Disease Foundation, Inc.:
Niemann-Pick Type C (NPC) is very different than Type A or B (ASMD). NPC Patients are not able to metabolize cholesterol and other lipids properly within the cell. Consequently, excessive amounts of cholesterol accumulate within the liver and spleen and excessive amounts of other lipids accumulate in the brain. NPC causes a secondary reduction of ASM activity, which led all three types to be considered forms of the same disease.
There is considerable variation in when Type C symptoms first appear and in the progression of the disease. Symptoms may appear as early as a few months of age or as late as adulthood.
Vertical gaze palsy (the inability to move the eyes up and down), enlarged liver, enlarged spleen, or jaundice in young children are strong indications that NPC should be considered. It is common for only one or two symptoms to appear in the early stages of the disease.
Type C Niemann-Pick Disease has an estimated 500 cases diagnosed worldwide. It is believed, however, that the number of people affected by NPC is higher, but diagnostic difficulties do not allow an accurate assessment of the occurrence rate. NPC has been initially diagnosed as a learning disability, mild retardation, “clumsiness,” and delayed development of fine motor skills. It is not uncommon for a family to spend several years seeking a diagnosis before NPC is identified.In most cases, neurological symptoms begin appearing between the ages of 4 and 10. Generally, the later neurological symptoms begin, the slower the progression of the disease.
NPC is always fatal. The majority of children with NPC die before age 20 (many die before the age of 10). Late onset of symptoms can lead to longer life spans but it is extremely rare for any person with NPC to reach age 40.
National Institute of Child Health and Human Development at the National Institutes of Health (NIH)
(once on the NICHD site, search “niemann-pick” without the quotation marks for links to articles, etc.)
The Progression of Niemann-Pick Disease — NNPDF parents tell their families’ stories in words and photographs
There is also some great information through the National Organization for Rare Disorders.
Doctor Dementia and the Dementia Adventure 
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