Thrombotic thrombocytopenic purpura or TTP is a rare blood clotting disorder where small clots form throughout blood vessels causing damage to red blood cells which encourages more clotting. The initial clotting is caused by the inhibition of an enzyme that is critical to breaking up blood clots together with the formation of antibodies which attack the enzyme. As a result, instead of breaking up quickly after any initial damage is repaired, clots continue to grow unabated, further damaging red blood cells.