Niemann-Pick disease type C
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Niemann-Pick disease type C
Genetics
Population genetics
Mendelian genetics and punnett squares
Hardy-Weinberg equilibrium
Inheritance patterns
Independent assortment of genes and linkage
Evolution and natural selection
Genetic disorders
Down syndrome (Trisomy 21)
Edwards syndrome (Trisomy 18)
Patau syndrome (Trisomy 13)
Fragile X syndrome
Huntington disease
Myotonic dystrophy
Friedreich ataxia
Turner syndrome
Klinefelter syndrome
Prader-Willi syndrome
Angelman syndrome
Beckwith-Wiedemann syndrome
Cri du chat syndrome
Williams syndrome
Alagille syndrome (NORD)
Achondroplasia
Polycystic kidney disease
Familial adenomatous polyposis
Familial hypercholesterolemia
Hereditary spherocytosis
Huntington disease
Li-Fraumeni syndrome
Marfan syndrome
Multiple endocrine neoplasia
Myotonic dystrophy
Neurofibromatosis
Treacher Collins syndrome
Tuberous sclerosis
von Hippel-Lindau disease
Albinism
Polycystic kidney disease
Cystic fibrosis
Friedreich ataxia
Gaucher disease (NORD)
Glycogen storage disease type I
Glycogen storage disease type II (NORD)
Glycogen storage disease type III
Glycogen storage disease type IV
Glycogen storage disease type V
Hemochromatosis
Mucopolysaccharide storage disease type 1 (Hurler syndrome) (NORD)
Krabbe disease
Leukodystrophy
Niemann-Pick disease types A and B (NORD)
Niemann-Pick disease type C
Primary ciliary dyskinesia
Phenylketonuria (NORD)
Sickle cell disease (NORD)
Tay-Sachs disease (NORD)
Alpha-thalassemia
Beta-thalassemia
Wilson disease
Fragile X syndrome
Alport syndrome
X-linked agammaglobulinemia
Fabry disease (NORD)
Glucose-6-phosphate dehydrogenase (G6PD) deficiency
Hemophilia
Mucopolysaccharide storage disease type 2 (Hunter syndrome) (NORD)
Lesch-Nyhan syndrome
Muscular dystrophy
Ornithine transcarbamylase deficiency
Wiskott-Aldrich syndrome
Mitochondrial myopathy
Autosomal trisomies: Pathology review
Muscular dystrophies and mitochondrial myopathies: Pathology review
Miscellaneous genetic disorders: Pathology review
Assessments
Niemann-Pick disease type C
USMLE® Step 1 questions
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Questions
USMLE® Step 1 style questions USMLE
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By Achim Fieß, Ömer Cal, Stephan Kehrein, Sven Halstenberg, Inez Frisch, Ulrich Helmut Steinhorst
Reproduced from Wikimedia Commons" style="max-height: 25px; max-width: 25px;">Wikimedia Commons
If further testing is performed, which of the following enzymes is most likely to be deficient in this patient?
Transcript
Niemann-Pick disease type C, or NPC, is a rare genetically inherited condition caused by mutations in either the NPC1 or NPC2 genes.
These mutations impair intracellular transport of cholesterol and other molecules, which causes progressive neurologic and developmental problems.
Now, cholesterol reaches the cells packed in lipoproteins, which bind to low density lipoprotein, or LDL, receptors on the cell membrane, to get inside the cell.
Then, cholesterol reaches the early-endosome, which is an intracellular organelle that eventually matures into a late-endosome, and finally into a lysosome.
Inside the lysosome, cholesterol is processed and recycled, so that it can be incorporated into the cell membrane.
To get out of the lysosome, first, cholesterol gets a little help from the NPC2 gene product, a protein that carries cholesterol up to the lysosomal membrane.
And on this membrane, cholesterol is greeted by the NPC1 gene product, which is a glycoprotein that moves cholesterol out of the lysosome and into the cell.
So with NPC1 or NPC2 mutations, intracellular cholesterol transport is impaired, so cholesterol accumulates inside lysosomes instead. Mutations can affect people of all ethnic backgrounds, and they’re inherited in an autosomal recessive pattern, which means that an affected individual must have two copies of the mutated gene, one from each parent.
Cholesterol buildup affects almost all cells, so it causes a variety of symptoms.
The brain and bone marrow are often affected.
The liver and spleen can be affected too, in which case, they enlarge.
Liver enlargement disrupts bile flow, causing bilirubin to accumulate in the blood.
This leads to jaundice, or yellow pigmentation of the skin and whites of the eye.
An enlarged spleen, on the other hand, may trap platelets, which causes easy bruising and bleeding issues.
Summary
Niemann-Pick disease type C is a rare genetically inherited condition, caused by mutations in the NPC1 or NPC2 genes. These mutations impair intracellular transport of cholesterol and other molecules, which causes progressive neurologic and developmental problems. This causes cholesterol to accumulate in lysosomes, resulting in brain, bone marrow, liver, spleen and lung damage.
Symptoms of Niemann-Pick disease type C typically begin in childhood and may include difficulty with movement and balance, difficulty swallowing, developmental delays, and progressive intellectual disability. There may also be hepatosplenomegaly, and liver failure.
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