Hereditary equine regional dermal asthenia
Hereditary equine regional dermal asthenia (HERDA), also known as hyperelastosis cutis (HC), is an inherited autosomal recessive connective tissue disorder. It develops from a homozygous recessive mutation that weakens collagen fibers that allow the skin of the animal to stay connected to the rest of the animal.
Source: Wikipedia — Hereditary equine regional dermal asthenia (CC BY-SA 4.0)