8. Characterisation of thrombocytopenia in APS

several reasons. The two main categories are the decreased thrombopoiesis in the bone mar-

CAPS: catastrophic antiphospholipid syndrome; HELLP: hemolysis, elevated liver enzymes, and low platelet count;

/L moderate and above 50 109

It is not only the number but also the thrombocyte function has a great importance in respect of consequences of thrombocytopenia: even a few thrombocytes can provide a satisfactory performance if the underlying disease does not diminish thrombocyte function. For example, in case of acute leukaemia patient may have bleeding even with a higher platelet number than that patient with immune thrombocytopenic purpura (ITP) who will be fine with a much

In case of the so-called consumptive thrombocytopenia, the basic phenomenon is the activation of platelets. Activation leads to thrombosis generation, factors of blood coagulation such as platelets are utilised and the thrombocyte number will decrease. As a secondary process

Thrombocytopenia is frequently found in patients with the APS and is usually mild (70–

aggressive treatment may be required. Low platelet counts usually appear associated with

The same working group has compared the frequency of thrombocytopenia in different subgroups of APS. They found no differences in the occurrence of low platelet number in patients

Thrombocytopenia is a frequent phenomenon of SLE. Increased concentrations of aPL antibodies have been found to be common in patients not only with SLE, but also with immune

other APS manifestations, but sometimes it may be the only sign of APS [35].

/L) and benign, with no intervention required. In a few cases it can be severe and

/L it is considered

/L mild thrombocytopenia [33].

row and the increased destruction of platelets in the peripheral blood [32]. Consequences depend on the degree of thrombocytopenia: under 20 109

Table 2. Mechanisms of thrombocytopenia in antiphospholipid antibody (aPL)-positive patients [34].

aHUS: atypical hemolytic uremic syndrome; TTP: thrombotic thrombocytopenic purpura.

severe, between 20 and 50 109

Increased platelet activation and destruction Immune-mediated (aPL-related, secondary ITP)

Drug-induced (e.g., heparin) Decreased platelet production Haemophagocytic syndrome Bone marrow necrosis Increased platelet pooling Pseudothrombocytopenia

58 Thrombocytopenia

Thrombotic microangiopathy (CAPS, HELLP syndrome, HUS, TTP)

lower thrombocyte count.

bleeding occurs (Table 2).

<sup>120</sup> <sup>10</sup><sup>9</sup>

6. Thrombocytopenia in APS

with primary or secondary APS [35].

Thrombocytopenia in APS is usually mild (70–<sup>120</sup> 109 /L) and does not require clinical intervention. In most of the cases, the main significance of thrombocytopenia is that it can be a sign, and when noticed it, the presence of aPL antibodies can be found. Severe thrombocytopenia (platelet count <50 109 /L) may be seen in 5–10% of patients [37].
