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Evolution and natural selection
Independent assortment of genes and linkage
Mendelian genetics and punnett squares
Alagille syndrome (NORD)
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Multiple endocrine neoplasia
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Treacher Collins syndrome
von Hippel-Lindau disease
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Glycogen storage disease type I
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Tay-Sachs disease (NORD)
Cri du chat syndrome
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Edwards syndrome (Trisomy 18)
Patau syndrome (Trisomy 13)
Fabry disease (NORD)
Glucose-6-phosphate dehydrogenase (G6PD) deficiency
Mucopolysaccharide storage disease type 2 (Hunter syndrome) (NORD)
Ornithine transcarbamylase deficiency
Autosomal trisomies: Pathology review
Miscellaneous genetic disorders: Pathology review
Muscular dystrophies and mitochondrial myopathies: Pathology review
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Isaiah Austin diagnosed with Marfan syndrome, basketball career over #SadNews
Marfan syndrome p. 50, 304
Marfan syndrome p. 722
Marfan syndrome as cause p. 304
Marfan syndrome p. 304
aortic aneurysms p. 733
aortic dissection and p. 307
cardiac defect association p. 304
cataracts p. 552
chromosome association p. 62
elastin and p. 50
heart murmur with p. 296
presentation p. 722
thoracic aortic aneurysms and p. 305
Marfan syndrome is a genetic disorder that results in defective connective tissue, which can affect a person’s skeleton, heart, blood vessels, eyes, and lungs.
Normally, the interstitial space of various body tissues is full of microfibrils - which are strong rope-like structures that provide tissue integrity and form connective tissue.
Each microfibril is made of cellulose as well as glycoproteins including the protein fibrillin. In some structures microfibrils form a scaffold for additional proteins like elastin.
Elastin fibers are highly cross-linked, and that gives them a rubber-band-like quality, which allows tissues to stretch and then spring back to their original shape.
Tissues that have elastin fibers are the arteries, skin, and lungs, and tissues that have microfibrils but no overlying layer of elastin are like tendons and the ciliary zonules that hold the eye lens in place.
These tissues are less stretchable, but still have considerable tensile strength.
In addition to being part of microfibrils, fibrillin also regulates tissue growth.
Fibrillin sequesters or removes transforming growth factor beta, or TGF-β, which stimulates tissue growth, so fibrillin therefore lowers how much TGF-β is available to stimulate growth.
Marfan syndrome is caused by mutations in a gene called FBN1, or fibrillin 1, on chromosome 15.
It’s autosomal dominant, which means that even if there’s a normal copy of the gene, a single mutated copy of the gene – in other words a heterozygous mutation – is sufficient to cause the disease.
The FBN1 gene encodes Fibrillin-1 protein, one of three fibrillin subtypes.
In Marfan syndrome, fibrillin-1 is either less abundant or it is dysfunctional. As a result, there are fewer functioning microfibrils in the extracellular matrix, and that means there’s less tissue integrity and elasticity.
Connective tissue is found throughout the body, so this can affect nearly every body system.
Additionally, TGF-β doesn’t get effectively sequestered, so TGF-β signaling is excessive in these tissues - meaning more growth.
The most obvious physical features of Marfan syndrome involve the skeleton.
The long bones grow excessively, so individuals are tall with long arms and legs – this is called a Marfanoid body habitus.
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