Niemann pick disease is an autosomal recessive inherited disease that affects
multiple body systems due to an individual’s sphingomyelin accumulating in their
lysosomal cells, affecting the spleen, liver, lungs, brain and bone marrow.
These cells play an important role in the transport of essential elements in
and out of the cell. There are four different types of Niemann Pick diseases
divided in types A, B, C1, and C2, which all vary in their severity of
symptoms. Each class has it’s own unique genetic cause and associated signs and
symptoms, and those affected are usually infants or adolescents.
Infants with type A develop hepatosplenomegaly
and fail to thrive, meaning they do not grow at the normal rate and failing to
gain weight. At around twelve months, they severely lack cognitive abilities
and experience psychomotor regression. In addition, they are affected with
interstitial lung disease, leading to respiratory failure because of the
recurring lung infections that they experience. This is all due to a mutation
in the SMPD1 gene, where the breakdown of sphingomyelin is deficient. Affected
individuals can be identified by their eye abnormalities, the cherry-red spot
and typically do not survive past early childhood.
Niemann Pick type B is similar to
type A in terms of signs and symptoms but it is less severe and individuals are
usually diagnosed during mid childhood. Affected individuals still experience hepatosplenomegaly
and frequent lung infections but they also have thrombocytopenia, a low
platelet count and delayed bone age. This disease occurs in an individual
because there is a mutation or variants of the SMPD1 gene. Approximately a
third of individuals have the cherry-red eye abnormality and experience
neurological impairment, but individuals usually make it to adulthood.
Lastly Niemann Pick type C1 and C2
are very similar, just differing in their genetic mutation. Type C1 is due to a
mutation in the NPC1 gene, whereas type C2 is a consequence of a mutation in
the NPC2 gene. Signs and symptoms of type C1 and C2 can become apparent at any
time, including during adulthood but typically become evident during childhood.
Individuals that are affected experience ataxia, vertical supranuclear gaze
palsy, dystonia, speech and swallowing difficulties that worsen with time, and
approximately one third of individuals affected experience seizures. Majority
of individuals affected with type C have type C1, making type C2 a rarer form. Those
with type C1 and type C2 may survive into adulthood.
There are no treatments for Niemann
Pick diseases, but symptoms can be treated with supportive care, such as a
pulmonologist for respiratory problems and a cardiologist for heart problems. Physiotherapy
is also essential for individuals affected with this disease because it will
help to maintain their fine motor skills and movement coordination. For type B,
cholesterol levels and liver function are monitored and individuals may undergo
a blood transfusion if their platelet count is too low and if their spleen is
enlarged. Individuals affected with mild to moderate type C may take the
miglustat drug, which is shown to improve neurological symptoms after taken
consistently for a two year period.
Niemann pick diseases type A and B can
be diagnosed through a blood or skin sample, which measures the amount of
sphingomyelinase an individual has in their white blood cells. An enzyme
analysis can also be conducted, where sphingomyelinase enzyme analyzed on dried
blood spots. To determine whether an individual has type C, a skin sample is
taken to observe how their cells store cholesterol and function. The filipin
test can also be used to diagnose type C because it evaluates the impaired
cholesterol in cultured cells.
As with all tests, there are pros
and cons and the genetic tests here are no exception. On one hand, if someone
undergoes a genetic test for Niemann Pick and they test positive, it will have
a huge psychologic toll on them and their lifestyle will have to completely
change. On the other hand, genetic tests offer a sense of security and comfort.
If Niemann Pick runs in the family and they’re worried their child might have
it, a genetic test might be a good option because if they test negative,
they’ll feel relieved and won’t have to constantly worry. Personally, I would
recommend getting a genetic test if an individual knows that they are a carrier
or if it runs in the family. The genetic test provides assurance and they won’t
have to speculate when they’re going to start showing symptoms or constantly
question whether their loved one is affected.