The blood

As APS is an autoimmune condition of the blood it is not surprising that the blood itself can be affected in several ways:

Low platelet count

A low or reduced platelet count, known medically as thrombocytopenia, is the most common blood related disorder found in APS patients.

Platelets are tiny cells that circulate in the blood and are essential in the formation of blood clots to control bleeding. The average life span of a platelet is ten days, but when they are lost from the circulation faster than they can be replaced from the bone marrow where they are made, the platelet count becomes low.

The platelet count in the circulating blood is normally between 150 and 400 per millilitre of blood. Some APS patients can experience a mild form of thrombocytopenia in which their platelet count is usually between 90 and 120. This slightly reduced platelet count does not tend to cause any problems other than a tendency to bruise easily.

However, in rare cases, the platelet count can fall to dangerously low levels (usually considered less than 50) that result in a condition known as immune thrombocytopenic purpura (ITP).

ITP was formerly known as idiopathic thrombocytopenic purpura as the underlying mechanism was unknown (idiopathic), but it is now recognised as an autoimmune disorder in which the immune system attacks and destroys the platelets.

The main symptom of ITP is spontaneous bleeding. On the skin this takes the form of red or purple pin-prick spots known either as purpura or petechiae (depending on their size, purpura being larger) caused by bleeding under the skin. Bleeding from the nose and gums is also quite common, while rare symptoms can include bleeding from the eyes, ears and stomach.

Paradoxically, this means that people with ITP and APS can have problems with excessive clotting and excessive bleeding.

For more information about ITP and the treatment available, please visit the ITP Support Association at


Anaemia is associated with a number of chronic conditions, including APS, and is caused by a low level of haemoglobin in the blood.

Haemoglobin is the iron-containing molecule in red blood cells that carries oxygen around the body. Therefore, low levels caused by anaemia result in less oxygen being delivered to the tissues. The common symptoms include lethargy, weakness, dizzy spells and feeling faint. If the anaemia becomes more severe, people may experience shortness of breath, palpitations and headaches.

A small minority of APS patients will also develop Evans syndrome, another autoimmune disorder which combines thrombocytopenia and autoimmune hemolytic anaemia. In Evans syndrome, antibodies destroy the red and white blood cells as well as the platelets.

Thrombotic thrombocytopenic purpura (TTP)

TTP is a rare and very serious blood condition in which very small clots form within the circulating blood; these clots then consume the platelets and cause the platelet count to drop. Antiphospholipid antibodies (aPL) have been found in a number of patients, but the exact association between TTP and APS is still unknown.


Leukopenia is a blood disorder where there is a decrease of the white blood cells in the circulating blood. It is commonly seen in other autoimmune conditions such as lupus and Sjogrens syndrome, but only rarely in APS patients.