Appendix 1: The most important connective tissue diseases.

Many different diseases are related to disorder in collagen. Type I collagen has been linked most definitively to heriditary diseases discussed here because this type has been studied in most detail. In this appendix a list is given of some of the most important diseases. In some cases an explanation is found for these disorder diseases. A medical solution was found seldom.

Syndrome Principal Clinical Features Molecular Pathology

Ehler-Danlos type I
Mild to severe hyperextensibility,
Hypotonic,
floppy infants,
Born prematurely, often with hernias,
Floppy ears,
Velvety, warm ,hyperextensible skin,
Thin atrophic corrugated scars after even minor trauma,
Pseudotumors in skin,
Varicose veins,
Hyper extensible joints leading to osteoarthritis,
Reversal of the spinal curves.
Unknown defects of collagen or other matrix proteins contribute to abnormal collagen fiber formation. Patients use supportion and have to build up strong muscle mass to protect joints.

Ehler-Danlos type II
Same as type I, but fewer of them and less severe.
Same as type I.

Ehler-Danlos type III
(=benign hypermobility syndrome)
Asymptomatic except for pain, rarely dislocation of joints in sports,
Symptoms present in 20s and 30s,
Joints laxity.
Unknown
Ehler-Danlos type IV
(ecchymotic or arterial)
Repeated arterial rupture leading to massive hematomas or sudden death,
Thin, soft, transparant skin with prominent venous patterns,
Rupture of viscera, including diverticula and the gravid uterus,
Very fragile tissues in surgery,
This often leads to a break of the aorta or intestinal canal.
Mutation within the type III collagen gene that result in production of a defective collagen molecule, the effect of the mutations are analogous to those in type I collagen that result in Osteogenesis Imperfecta.
This leads to defective transcription or translation (DNA-code =>protein) of type-III-collagen.

Ehler-Danlos type V and IX
Not well characterized but general sporadic features of type I and II.
In type IX occipital horns (bony spurs) have been found.
Perhaps an abnormality of copper metabolism.

Ehler-Danlos type VI
(ocular)
Several scoliosis,
Joint dislocations,
Hyper extensible skin and joints,
Diminished muscle mass,
Microcornea,
Retinal detachment and glaucoma,
Tearing of the cornea,
Other changes similar to Ehler-Danlos type I.
Decreased hydroxylysine content in type I collagen of skin and bone (type II collagen is normal) due to defective lysyl hydroxylase activity. A consequence of low hydroxylysine level is altered cross-linkage of collagen within bone. High doses of ascorbic acid (Vit. C) to increase the lysyl hydroxylase affinity for substrate. The resulting hydroxylysine has to work twice as good.

Ehler-Danlos type VII
(=arthrochalasis multiplea congenita)
Pronounced joints hypermobility,
Moderate cutuneom elasticity,
Moderate bruising, round faces,
Short stature,
Multiple dislocations of large joints,
Frequently occuring luxations.
Abnormal accumulation of procollagen in tissue due to defective and lower enzymatic cleavage of the precursor to its mature form. Most cases result from an "exon skip" during collagen mRNA processing that deletes the cleavage site within the protein, point mutation at the cleavage site, or Mutations elsewere in the molecule that cause misalignment of the three α-chains within the cleavage site.

Ehler-Danlos type VIII
Severe resorption periodontitis with loss of teeth,
Marked fragility of the skin without hyper elasticity.
Unknown.

Lathyrism
Hypermobile joints,
Very extensible skin,
Looks the same as Ehler-Danlos type V.
Poisoning with b-aminopropionitrile (present in the sweat pea plant) inhibits transformation of lysyl side chains into aldehydes by forming a tight complex with lysyl oxidase. The collagen is extremely fragile because of a deficiency of lysyl oxidase.

Dermatosparaxis
(a cattle dissease)
Very fragile dermis.
This disease is caused by an absence of some procollagen peptidase. Fragile because it contains disorganical collagen bundles, build with collagen that still possess the N-term propeptides.

Mild Osteogenesis Imperfecta
(=Sillence type I)
Prominent frontal bones and narrow mandible,
Loss of hearing after age 20,
Usually no fracture at birth but 5-15 fractures before puberty, then fewer in adulthood, fractures heal well,
Radiological osteoporosis,
May masquerade as child abuse.
Null a-I(I) allele possibly due to a defect in mRNA splicing, premature stop codon, or frame shift mutation. The effect is a reduced collagen synthesis for the affected allele, the collagen that accumulates in the tisssues arises from the remaining normal allele. This bone disease is mild because the collagen in the matrix is reduced in quantity but the structure is normal. After puberty, the fracture incidence decreases as less new connective tissue is formed.

Lethal Osteogenesis Imperfecta
(=Sillence type II)
Multiple intrauterine fractures,
Death within 1 week of birth usually from diminished respiratory reserve,
Skeletal deformities arising from multiple fractures due to brittle bones.
Deletions or substitutions in one of the a1(I)-chain genes are leading to destabilization of the collagen helix. The triple helix structure is disrupted near the end, exposing it to excessive hydroxylation and glycosylation. Because of this reason the collagen is partly unfolded at body temperature and can not form highly ordered fibrillar arrays. For example: Mutation of a single glycine in collagen can be lethal. In this case only one nucleotide is different:
CCT GGT CCT CGC GGT CGC ACT GGT
Pro Gly Pro Arg Gly Arg Thr Gly
CCT TGT CCT CGC GGT CGC ACT GGT
Pro Cys Pro Arg Gly Arg Thr Gly

Scurvy
A vivid description of this disease was given by Jacques Cartier in 1536, when it afflicted the crew of his expedition:
Some did lose all their strength, and could not stand on their feet.... Other also had all their skins spotted with spots of blood of apurple colour: then did it ascend up to their ankles, knees, thighs, shoulders, arms, and necks. Their mouth became stinking, their gums so rotten, that all the flesh did fall off, even to the roots of the teeth, which did also almost all fall out.
It is nowadays commonly known that scurvy is prevented by eating vitamin C. This way scurvy may be regarded as a hereditary metabolic disease and the addition of dietary ascorbic acid may be regarded as therapeutic. Because the treat is universal in man and is so easily corrected, it is frequently not even included in comprehensive reviews of inherited metabolic diseases. The pathway of the biosynthesis of ascorbic acid was elucidated at the end of the sixties (Nishikimi and Udenfriend, 1977):
D-glucose =>(1)=> D-glucuronic acid =>(2)=> L-gulonic acid =>(3)=> L-gulonolactone =>(4)=> L-ascorbic acid
Steps 2 and 3 are catalysed by enzymes in the liver. Step 4 is catalysed by L-gulonolactone oxidase, an enzyme in little microsomes. Animals which are scurvy-prone lack this L-gulonolactone oxidase activity. All of the other enzymes in the pathway were found. When scurvy-prone men and aminals have shortage of ascorbic acid, the enzym propyl hydroxylase doesn't function proper anymore. Insufficient hydroxylation of collagen takes place which lead to less thermostabile collagens. Because the melting temperature of the collagens is probably reduced below 37°C it is unlikely that they could remain helical at body temperature. Scurvy patients are actual melting (see also chapter 2).

Syndrome	Principal Clinical Features	Molecular Pathology
Ehler-Danlos type I	Mild to severe hyperextensibility, Hypotonic, floppy infants, Born prematurely, often with hernias, Floppy ears, Velvety, warm ,hyperextensible skin, Thin atrophic corrugated scars after even minor trauma, Pseudotumors in skin, Varicose veins, Hyper extensible joints leading to osteoarthritis, Reversal of the spinal curves.	Unknown defects of collagen or other matrix proteins contribute to abnormal collagen fiber formation. Patients use supportion and have to build up strong muscle mass to protect joints.
Ehler-Danlos type II	Same as type I, but fewer of them and less severe.	Same as type I.
Ehler-Danlos type III (=benign hypermobility syndrome)	Asymptomatic except for pain, rarely dislocation of joints in sports, Symptoms present in 20s and 30s, Joints laxity.	Unknown
Ehler-Danlos type IV (ecchymotic or arterial)	Repeated arterial rupture leading to massive hematomas or sudden death, Thin, soft, transparant skin with prominent venous patterns, Rupture of viscera, including diverticula and the gravid uterus, Very fragile tissues in surgery, This often leads to a break of the aorta or intestinal canal.	Mutation within the type III collagen gene that result in production of a defective collagen molecule, the effect of the mutations are analogous to those in type I collagen that result in Osteogenesis Imperfecta. This leads to defective transcription or translation (DNA-code =>protein) of type-III-collagen.
Ehler-Danlos type V and IX	Not well characterized but general sporadic features of type I and II. In type IX occipital horns (bony spurs) have been found.	Perhaps an abnormality of copper metabolism.
Ehler-Danlos type VI (ocular)	Several scoliosis, Joint dislocations, Hyper extensible skin and joints, Diminished muscle mass, Microcornea, Retinal detachment and glaucoma, Tearing of the cornea, Other changes similar to Ehler-Danlos type I.	Decreased hydroxylysine content in type I collagen of skin and bone (type II collagen is normal) due to defective lysyl hydroxylase activity. A consequence of low hydroxylysine level is altered cross-linkage of collagen within bone. High doses of ascorbic acid (Vit. C) to increase the lysyl hydroxylase affinity for substrate. The resulting hydroxylysine has to work twice as good.
Ehler-Danlos type VII (=arthrochalasis multiplea congenita)	Pronounced joints hypermobility, Moderate cutuneom elasticity, Moderate bruising, round faces, Short stature, Multiple dislocations of large joints, Frequently occuring luxations.	Abnormal accumulation of procollagen in tissue due to defective and lower enzymatic cleavage of the precursor to its mature form. Most cases result from an "exon skip" during collagen mRNA processing that deletes the cleavage site within the protein, point mutation at the cleavage site, or Mutations elsewere in the molecule that cause misalignment of the three α-chains within the cleavage site.
Ehler-Danlos type VIII	Severe resorption periodontitis with loss of teeth, Marked fragility of the skin without hyper elasticity.	Unknown.
Lathyrism	Hypermobile joints, Very extensible skin, Looks the same as Ehler-Danlos type V.	Poisoning with b-aminopropionitrile (present in the sweat pea plant) inhibits transformation of lysyl side chains into aldehydes by forming a tight complex with lysyl oxidase. The collagen is extremely fragile because of a deficiency of lysyl oxidase.
Dermatosparaxis (a cattle dissease)	Very fragile dermis.	This disease is caused by an absence of some procollagen peptidase. Fragile because it contains disorganical collagen bundles, build with collagen that still possess the N-term propeptides.
Mild Osteogenesis Imperfecta (=Sillence type I)	Prominent frontal bones and narrow mandible, Loss of hearing after age 20, Usually no fracture at birth but 5-15 fractures before puberty, then fewer in adulthood, fractures heal well, Radiological osteoporosis, May masquerade as child abuse.	Null a-I(I) allele possibly due to a defect in mRNA splicing, premature stop codon, or frame shift mutation. The effect is a reduced collagen synthesis for the affected allele, the collagen that accumulates in the tisssues arises from the remaining normal allele. This bone disease is mild because the collagen in the matrix is reduced in quantity but the structure is normal. After puberty, the fracture incidence decreases as less new connective tissue is formed.
Lethal Osteogenesis Imperfecta (=Sillence type II)	Multiple intrauterine fractures, Death within 1 week of birth usually from diminished respiratory reserve, Skeletal deformities arising from multiple fractures due to brittle bones.	Deletions or substitutions in one of the a1(I)-chain genes are leading to destabilization of the collagen helix. The triple helix structure is disrupted near the end, exposing it to excessive hydroxylation and glycosylation. Because of this reason the collagen is partly unfolded at body temperature and can not form highly ordered fibrillar arrays. For example: Mutation of a single glycine in collagen can be lethal. In this case only one nucleotide is different: CCT GGT CCT CGC GGT CGC ACT GGT Pro Gly Pro Arg Gly Arg Thr Gly CCT TGT CCT CGC GGT CGC ACT GGT Pro Cys Pro Arg Gly Arg Thr Gly
Scurvy	A vivid description of this disease was given by Jacques Cartier in 1536, when it afflicted the crew of his expedition: Some did lose all their strength, and could not stand on their feet.... Other also had all their skins spotted with spots of blood of apurple colour: then did it ascend up to their ankles, knees, thighs, shoulders, arms, and necks. Their mouth became stinking, their gums so rotten, that all the flesh did fall off, even to the roots of the teeth, which did also almost all fall out.	It is nowadays commonly known that scurvy is prevented by eating vitamin C. This way scurvy may be regarded as a hereditary metabolic disease and the addition of dietary ascorbic acid may be regarded as therapeutic. Because the treat is universal in man and is so easily corrected, it is frequently not even included in comprehensive reviews of inherited metabolic diseases. The pathway of the biosynthesis of ascorbic acid was elucidated at the end of the sixties (Nishikimi and Udenfriend, 1977): D-glucose =>(1)=> D-glucuronic acid =>(2)=> L-gulonic acid =>(3)=> L-gulonolactone =>(4)=> L-ascorbic acid Steps 2 and 3 are catalysed by enzymes in the liver. Step 4 is catalysed by L-gulonolactone oxidase, an enzyme in little microsomes. Animals which are scurvy-prone lack this L-gulonolactone oxidase activity. All of the other enzymes in the pathway were found. When scurvy-prone men and aminals have shortage of ascorbic acid, the enzym propyl hydroxylase doesn't function proper anymore. Insufficient hydroxylation of collagen takes place which lead to less thermostabile collagens. Because the melting temperature of the collagens is probably reduced below 37°C it is unlikely that they could remain helical at body temperature. Scurvy patients are actual melting (see also chapter 2).

Collagen related diseases might look very exceptional. Nevertheless, only in England there are already 6000 man suffering from inheritable collagen diseases. Also a broad time scale should be considered in examining the effects of mutations in collagen genes. Mutations that do not have any immediate consequence early in life may well lead to slowly manifesting chronic diseases such as osteoporosis or osteoarthritis. The picture on the back-page is taken from a patient suffering from Ehlers-Danlos syndrome ( Light and Bailey, 1979). Some different mutations may produce similar clinical phenotypes. This is termed 'genetic heterogeneity'.