Thrombasthenia is an inherited bleeding disorder affecting dogs. Affected dogs have abnormal platelet activity. Platelets are blood cells that are necessary for the normal clotting of blood. Affected dogs usually present between 3 and 6 months of age with bleeding gums as their permanent teeth are erupting. Affected dogs often have recurrent nose bleeds until approximately 2 years of age. Affected dogs may also have skin bruising and increased and prolonged bleeding after surgery, after trauma and when in heat. The prognosis for affected dogs is good, but they are usually smaller than normal for their breed and must receive iron supplementation to prevent deficiency which can occur during growth or periods of chronic bleeding.