Objectives: We aimed to characterise the frequency of thrombocytopenia in systemic lupus erythematosus (SLE) and determine its time of onset during the course of the disease, and its severity and impact on mortality.
Methods: This was a single-centre cohort analysis of 707 patients with SLE followed for up to 40 years. We reviewed the patients' clinical notes identifying the presence of thrombocytopenia, its time of onset and ascertained other clinical and serological features of the disease. Thrombocytopenia was classified as mild (100-149x109/L), moderate (31-99x109/L) or severe (≤30x109/L platelets). It was also classified as asymptomatic, with minor bleeding or with major bleeding.
Results: 22.9% of patients (n=162) had thrombocytopenia prior to or during the course of SLE. Twenty-three patients (14.2%) had isolated immune thrombocytopenia (ITP) before the diagnosis of SLE. Median follow-up time was 19 years (IQR=13). Most patients (n=67, 41.4%) had mild thrombocytopenia. More than half the patients (n=98, 60.5%) developed asymptomatic thrombocytopenia and only 6 patients (3.7%) had major bleeding events in the context of thrombocytopenia. The development of severe thrombocytopenia any time during the course of SLE was associated with an increased risk of death (HR=3.57, p=0.025). Anti-phospholipid syndrome was over twice as common in patients with thrombocytopenia in the cohort. There is an increased risk of death for male patients (HR=3.41, p=0.036) who develop thrombocytopenia and for those who present with concomitant haemolytic anaemia (HR=3.07, p=0.027).
Conclusions: The presence of severe thrombocytopenia (platelets ≤30x109) in patients with SLE is associated with an increased risk of death, regardless of bleeding events. Male patients with SLE and thrombocytopenia have an increased mortality risk, as have those who develop concomitant thrombocytopenia and haemolytic anaemia.