Cutaneous asthenia (Ehlers-Danlos syndrome, rubber puppy disease) is caused by a defect in the maturation of type I collagen. This causes weak structural support of blood vessels and can result in hematoma formation and easy bruising. The disorder has been reported in dogs, cats, mink, horses, cattle, sheep, and people but is rare in domestic animals. The most striking clinical abnormality is loose, hyperextensible skin that tears easily. No treatment is available.
Several diseases cause severe, often generalized vasculitis and are characterized by bleeding disorders.
Rocky Mountain spotted fever (see Rocky Mountain Spotted Fever) is caused by Rickettsia rickettsii, which is transmitted by the ticks Dermacentor variabilis and D andersoni. The rickettsial organisms invade endothelial cells and cause cellular death with resultant perivascular edema and hemorrhage. Variable degrees of coagulation cascade activation can occur along with thrombocytopenia. Infected dogs may have epistaxis, petechial and ecchymotic hemorrhages, hematuria, melena, or retinal hemorrhages. In severely affected dogs, disseminated intravascular coagulation may occur.
Canine herpesvirus generally affects puppies 7–21 days old. Generalized necrotizing vasculitis is accompanied by perivascular hemorrhage. The disease is usually rapidly fatal, and most puppies die within 24 hr after showing signs.