Spondylodysplastic Ehlers-Danlos syndrome

Alternate names

Proteodermatan sulfate, defective biosynthesis of; PDS, defective biosynthesis of; Dermatan sulfate proteoglycan; Xylosylprotein 4-beta-galactosyltransferase deficiency; XGPT deficiency; Galactosyltransferase 1 deficiency; Ehlers-Danlos syndrome, progeroid type (former)

Definition

Spondylodysplastic Ehlers-Danlos syndrome (EDS) is a subtype of the EDS, a group of genetic disorders of the connective tissue, which is the material between body cells that gives tissues form and strength. Ehlers-Danlos syndromes primarily affects the skin, hair, and skeletal system.

Cause

• Spondylodysplastic Ehlers-Danlos syndrome (spEDS) can be caused by changes (mutations) in both of a person's copies of the B4GALT7 gene, which is located on chromosome 5. This gene provides instructions for making an enzyme that is involved in the production of collagen (the main protein in connective tissue). When not enough enzyme is made by the B4GALT7 genes, collagen is not formed correctly in connective tissue. The symptoms of the disorder are caused by weak connective tissue. Researchers are still studying exactly how mutations in the B4GALT7 gene cause the signs and symptoms.
• Some cases are caused by mutations in the B3GALT6 gene. People with mutations in this gene may have kyphoscoliosis, joint hypermobility, contractures, peculiar face, slender and tapered fingers, abnormal teeth, osteoporosis, aortic aneurisms, and lung problems. The B3GALT6 gene encodes a protein that is part of the connective tissue.
• Other cases are caused by mutations in the SLC39A13 gene. These cases are characterized by protuberant eyes, wrinkled palms of the hands, tapering fingers, and hypermobility of distal joints. It is not known how mutations in this gene result in the symptoms. The SLC39A13 gene produces a protein that regulates the entrance of zinc into cells.

Inheritance

Autosomal recessive inheritance, a 25% chance

Spondylodysplastic Ehlers-Danlos syndrome is inherited in an autosomal recessive pattern. This means that an individual must have two non-functional copies of the gene to be affected. One copy is inherited from each parent. If an individual has only one non-functional copy (such as each parent), he or she is a "carrier." Carriers do not typically show any signs or symptoms of a recessive condition. When two carriers of a recessive condition have children, with each pregnancy there is a 25% chance for the child to be affected, a 50% chance for the child to be a carrier (like each parent) and a 25% chance that the child will be unaffected and also not be a carrier. An individual with a recessive condition will generally have unaffected children, except in the rare circumstance where his or her partner is a carrier of the same mutated gene.

Signs and symptoms

Common symptoms of spondylodysplastic Ehlers-Danlos syndrome include:

• Progressive short stature in childhood, which can result in short stature as an adult (less than 152cm)
• Poor muscle tone (hypotonia), ranging from severe and present from birth, to mild and later-onset
• Bowing of limbs

Other symptoms include:

• Skin hyperextensibility; soft, doughy skin; thin, translucent skin
• Pes planus (flat feet)
• Delayed motor development
• Fragile bones from low bone mineral density (osteopenia)
• Mild intellectual disabilities or learning disabilities
• Eye problems
• Characteristic facial features (triangular face, wide-spaced eyes, proptosis ("bulging" eyes), narrow mouth, low-set ears, sparse scalp hair, flat face, wide forehead, blue sclerae, abnormal teeth, and cleft palate/bifid uvula)
• Thin, curly hair; sparse eyebrows and eyelashes
• Joint contractures and hypermobility
• Loose, elastic skin on the face
• The former name for spondylodysplastic Ehlers-Danlos syndrome was "EDS, progeroid type." Although "progeroid" means "appearance similar to old age," affected people do not actually have premature aging and are not expected to have a shortened life span.

Diagnosis

• Spondylodysplastic EDS is characterized by short stature (progressive in childhood), muscle hypotonia (ranging from severe congenital, to mild later-onset), and bowing of limbs. It can be caused by variations in both copies of the B4GALT7 gene.
• Other cases can be caused by variations in the B3GALT6 gene. People with variations in this gene can have kyphoscoliosis, tapered fingers, osteoporosis, aortic aneurysma, and problems with the lungs.
• Other cases can be caused by the SLC39A13 gene. Those with variations in this gene have protuberant eyes, wrinkled palms of the hands, tapering fingers, and distal joint hypermobility.

Treatment

• People with spondylodysplastic Ehlers-Danlos syndrome can benefit from a variety of treatments depending on their symptoms.
• Affected children with weak muscle tone and delayed development might benefit from physiotherapy to improve muscle strength and coordination. People with joint pain might benefit from anti-inflammatory medications.
• Lifestyle changes or precautions during exercise or intense physical activity may be advised to reduce the risk of accidents involving the skin and bones. It is recommended that affected individuals discuss treatment options with their healthcare provider.

NIH genetic and rare disease info

• NIH info on Spondylodysplastic Ehlers-Danlos syndrome

Spondylodysplastic Ehlers-Danlos syndrome is a rare disease.

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