ENFERMEDAD DE NIEMANN PICK
There are three recognised forms of Niemann-Pick Disease, Niemann-Pick Type A, B and C. Niemann-Pick Type A and B are caused by an enzyme deficiency, causing a build up of toxic materials in the body's cells. Niemann-Pick Type C is not caused by an enzyme deficiency, but the end result is the same; an accumulation of materials (cholesterol and otherfatty acids) in the body's cells.
In Niemann-Pick Type A this accumulation occurs very quickly, an affected child will usually die before reaching three years of age.
Niemann-Pick Type B does not affect the brain and, although growth may be slow, those affected will survive into adolescence or early adulthood, with many being able to lead a full and normal life.
In Niemann-Pick Type C, thebrain and other organs are affected, leading to progressive intellectual decline, loss of motor skills, seizures and dementia. Speech can become slurred and swallowing problems may develop. The rate at which the disease progresses varies greatly between patients; children who develop neurological symptoms in early childhood are thought to have a more aggressive form of the disease, others mayremain symptom free for many years.
Why is it called Niemann-Pick?
The Niemann-Pick diseases are quite separate in terms of the fundamental cause but the similarities in clinical presentation have resulted in the naming of the diseases as Niemann-Pick, after two doctors who described the symptoms in the early part of the 20th century.
In 1914, a German paediatrician, Dr Albert Niemann,described the clinical presentation of children with the disease, but at that time little was known regarding the cellular or molecular explanation. Then, in the 1920's, the studies of Luddwick Pick provided evidence of a new disorder, one distinct from storage disorders previously described. Further investigations using cells taken from the tissues of affected individuals in the mid and latter years ofthe century, resulted in an improved understanding of the diseases and their cause. Since then there has been a considerable amount of investigation into these and other inherited diseases of metabolism.
It was not until 1958 that the disease presentations were classified into type A, B and C. In 1966 types A and B were identified with a lysosomal enzyme, acid sphingomyelinase. Type C, which inturn was further sub classified into types D, E and possibly others, remained the subject of investigation, mainly by the National Institute of Health near Washington, USA. Although NPC could be diagnosed through clinical, histological and biochemical means, it was not until 1997 that the genetic link was made which accounted for most of the NPC cases and is identified as NPC1. Subsequently, afurther link was made with a second gene, NPC2, which accounted for most of the remainder. Some patients diagnosed with the disease remain to be accounted for. All known types of Niemann-Pick disease are acquired through autosomal recessive inheritance.
What causes Niemann-Pick disease?
In order to appreciate the cause of the disease, some basic understanding of the biology of the cell is needed.This is a complicated subject but it is worth investing a little time to learn about the basic components of the cell and gain a general understanding into how inheritance works.
How does a person become affected by Niemann-Pick disease?
Niemann-Pick is an inherited disease. It is inherited in an autosomal recessive manner. In simple terms, this means that both parents have to be carriers ofthe faulty gene. In each pregnancy of a carrier couple, there is a 25% chance that they will pass on this gene mutation to their child.
Autosomes are the non-sex related chromosomes, and recessive indicates that the effects of possessing a single copy of a disease-causing gene are hidden. With a recessive condition, a person may be a carrier of a disease gene, but with no noticeable affect...