Eleven subtypes are now recognized and this com-plicated subject has earned its own scientific group, which continuously updates classification and mole-cular biology.
All varieties of the Ehlers–Danlos syndrome are based on abnormalities in the formation or modification of collagen and the extracellular matrix, but are not necessarily a result of mutations in the collagen genes themselves. Established defects include lysyl hydroxy-lase deficiency, abnormalities in pro-alpha-1 (V) col-lagen chains, mutations in type III collagen genes, a deficiency of procollagen protease, and a fibronectin defect.
• Hyperelasticity of the skin.
• Hyperextensibility of the joints.
• Fragility of skin and blood vessels.
• Easy bruising.
• Curious (‘cigarette paper’) scars.
These depend on the type. They include subluxation of joints, varicose veins in early life, an increased liability to develop hernias, kyphoscoliosis, aortic aneurysms and ruptured large arteries, and intraocu-lar haemorrhage. Affected individuals may be born prematurely as a result of the early rupture of fragile fetal membranes.
The diagnosis is made on the clinical features and family history. The frequent skin lacerations and pro-minent scars may suggest child abuse. The diagnosis and type can sometimes be confirmed by enzyme studies on isolated fibroblasts. There is no effective treatment but genetic counselling is needed.