Final answer:
Skin fragility in older animals with Ehlers-Danlos syndrome is primarily caused by the deterioration of type-III collagen due to enzyme deficiencies or mutations in collagen synthesis, leading to decreased skin elasticity and resilience.
Step-by-step explanation:
The cause of skin fragility in older animals with Ehlers-Danlos syndrome (EDS) is attributed to the progressive deterioration of collagen, particularly type-III collagen. This deficiency may be due to the lack of the enzyme hydroxylase or mutations in the amino acid sequences during collagen synthesis. Collagen is a critical component of the extracellular matrix that provides structural support to the skin and other tissues, and its deterioration leads to the characteristic symptoms of EDS including skin and vascular problems.
Ehlers-Danlos syndrome affects different parts of the body such as joints, heart valves, organ walls, arterial walls, etc. In the skin, these problems manifest as increased fragility, decreased elasticity, slow wound healing, and a tendency to bruise easily. The reduction in collagen and elastin production over time, especially as animals age, compromises the skin's strength and resilience.