Cutaneous Asthenia in Dogs
Cutaneous asthenia (literally, weak skin) is part of a group of hereditary disorders characterized by skin that is unusually stretchy and droopy. It is caused by a genetic mutation that is passed from parent to offspring. More than one genetic disorder is suspected, but this condition cannot be determined by skin and tissue samples, it is diagnosed through observation.
This condition is also known as Ehlers-Danlos syndrome, a disease characterized by deficient levels of collagen, the protein molecule necessary for providing strength and elasticity to the skin and ligaments, along with much of the rest of the body. Collagen is the “glue” that holds the body together. A lack of collagen will result in abnormal collagen synthesis and fiber formation.
Dogs affected with this disorder suffer from painful dislocation at the joints due to the instability of the ligament fibers that hold the bones to each other. The ligaments stretch with movement, but without the elasticity needed to return to their form they stay stretched out, allowing the bones to pop out of their connective joints. This creates a painful physical environment for the sufferer of cutaneous asthenia.
The lack of collagen also affects the structure of the skin. Without elasticity, the skin does not return to the body when it has been stretched away from the body, eventually drooping heavily. This lack also weakens the skin's resilience, making it easy to injure and prone to tearing, bruising and scarring.
This disease is rare, and has been clearly identified in only a small number of dogs. Patients are usually diagnosed at a young age.
The condition or disease described in this medical article can affect both dogs and cats. If you would like to learn more about how this disease affects cats, please visit this page in the PetMD health library.
Symptoms and Types
The symptoms of cutaneous asthenia generally include saggy skin, with extra (redundant) folds of skin; the skin is very soft and delicate, thin, and with little elasticity. The skin is easily torn, often with wide “fish mouth” type wounds that bleed very little, but leaving scars that widen over time. There may also be scars on the skin that are unaccounted for. Your dog may have swelling under the skin of the elbows, due to the bones putting pressure on the skin when the dog is at rest, and bruising and bleeding under the skin (hematoma) of the elbows and throughout the body. Lacerations on the back and head are common. Collagen is low internally as well as externally, making it possible for internal structures to rupture, with resultant internal bleeding.
With dogs, this condition commonly causes loose joints, which can vary from mild to severe. The joints may be only slightly loose, making mobility a challenge, or the joints may be loose to the point that the bones are dislocated. This can be bones of the legs, hips, and other parts of the body that are connected by joints. Rare, but also an effect this condition has on dogs, is dislocation of the eye lens. This is caused by the same lack of collagen, in this case affecting the ligaments that hold the lens in place.
This condition occurs in the following breeds:
- Dachshunds - miniature and standard
- English setters
- English springer spaniels
- German shepherds
- Irish setters
- Manchester terriers
- Red kelpies
- Springer Spaniel
- St. Bernards
- Welsh corgis
The primary cause of this medical condition is heredity. It is caused by a genetic mutation that is passed from parent to offspring, and can be either dominant – from both parents, or recessive – from only one parent. In the dominant form, both parents are carriers of the mutated gene, with neither dog showing symptoms. With the recessive form, one parent may be a carrier, with no symptoms present. In either case, it is generally advised that the parents of an affected animal not be used for further breeding, and that the siblings of the affected animal also be held back from breeding.
An examination of the skin's extensibility is performed by stretching the skin to its full ability, observing any lack of discomfort in the dog, and measuring the extent the skin stretches to. The resulting measurements are based on the Skin Extensibility Index (SEI), which measures the skin that has been stretched (using the dorsal skin on the back), divided by the dog's length from the back crest of the skull to the base of the tail. The numerical value that is found determines the severity of the condition. The expected numbers are an index of higher than 14.5 percent.