Immune thrombocytopenia (ITP) is a bleeding disorder mediated by an overactive immune system. Patients experience a higher risk of bleeding due to falling platelet count; this is due to the complex interaction of humoral and cellular immune abnormalities that cripple the body’s ability to keep up with platelet production (platelet count < 100 x 109/L).
Prior to diagnosis, patients can often be asymptomatic or experience mild mucocutaneous hemorrhage. In around 5% to 6% of individuals, severe bleeding occurs, prompting urgent investigations into its causes, making it more likely that the patient receives a diagnosis of ITP. Patients who are asymptomatic are usually diagnosed with this disorder much later in life.
Read more about ITP etiology
When talking about platelet count, we are in essence talking about destruction and supply. For the body to have normal levels of platelets, there must be a sort of equilibrium between platelet clearance and platelet production. In ITP, this balance is severely disrupted; platelets are destroyed excessively, and new platelets cannot be formed. This dangerous dip in platelet levels means that they are insufficient for blood clotting should a bleeding episode occur. Other hallmarks of ITP are T-cell cytotoxicity and impaired megakaryopoiesis.
There is no “gold standard” diagnostic test for ITP; rather, it is a diagnosis of exclusion, meaning that its presence is only suspected once more likely diagnoses have been clinically ruled out. This inadvertently means that ITP is low in the list of one’s differentials, making it more likely that it is missed out altogether.
Chinese guidelines encourage bone marrow examinations and tests to be carried out for diagnostic purposes. This will arm physicians with more information to rule out some diseases outright. In addition, bone marrow studies can drastically shorten time to diagnosis.
Therapeutic Options to Consider
Corticosteroids remain the “initial cornerstone therapy for patients with ITP without relative contraindications,” according to Liu and colleagues in the Journal of Hematology & Oncology.
The most commonly used corticosteroid is oral prednisolone, around 0.5 mg – 2 mg/kg/day for the first weeks, followed by gradual tapering with the aim to stop by week 6 to 8. Because long-term steroid use is associated with adverse effects, some propose that dexamethasone be given at high doses for a shorter period of time instead (40 mg daily for 4 days).
Intravenous immunoglobulin (IVIG) is also used as a first-line therapy for ITP, with or without corticosteroids. Studies indicate that it is highly effective, raising the platelet count rapidly in more than 80% of patients who were newly diagnosed with this disease. The downsides to this form of therapy is that it is expensive, and the response, while impressive, is often transient.
“It is notable that IVIG is a blood product that is sometimes in short supply and therefore should be used sparingly,” Liu et al wrote. “The decision on IVIG treatment initiation ought to depend mainly on the bleeding severity grade rather than the platelet count.”
Another commonly prescribed therapy for countering ITP is anti-D immunoglobulin; as its name suggests, it is an immunoglobulin directed against the D antigen of the Rhesus (Rh) blood group system. This form of therapy is effective specifically in Rh-positive patients who still have an intact spleen. Studies indicate that it achieves an overall response rate of 65% and that this is sustained for roughly a month.
In the event of an emergency (ie, a patient suffers from life-threatening bleeding), the goal is to increase the platelet count with great speed; studies indicate that a combination of drugs achieve this best. These include: IVIG, intravenous corticosteroids, platelet transfusion, and general supportive care. Physicians should also prescribe relevant medications to stop the site of bleeding: antifibrinolytics often work, and oral contraceptives may be used in female patients with menorrhagia.
From the Past to the Future
Epidemiological studies indicate that the COVID-19 pandemic probably caused the rise in ITP incidence and exacerbated the condition of existing patients. There has been much research into how COVID-19 manifests in patients with ITP, and 1 thing that scientists have learned is that COVID-19 infection increases the risk of thrombotic complications, which has led to a renewed push for vulnerable patients to receive proper thromboprophylactic care in the hospital.
Future studies continue to explore the merits of either new drugs or different combinations of existing drugs. However, due to the heterogeneity in the population of patients with ITP, appropriate caution should be taken when analyzing these study results. Among the treatment combinations under study are a mix of immunosuppressants with thrombopoietin receptor agonists, as well as rituximab with recombinant human thrombopoietin.
Read more about ITP treatment
There is also a need to continue conducting studies on existing trials to see if their dose and frequency are optimized, as well as to investigate their effect on long-term outcomes. Because many of the drugs used to treat ITP are relatively new, it is important that long-term studies are carried out to see their effects over the course of decades.
Overall, current therapies for chronic ITP are mostly able to return platelet count to normal, with a small proportion requiring additional treatment. Further exploration of therapeutic possibilities should offer both clinicians and their patients more options to choose from in the near future.
Reference
Kim DS. Recent advances in treatments of adult immune thrombocytopenia. Blood Res. Published April 30, 2022. doi:10.5045/br.2022.2022038
Liu XG, Hou Y, Hou M. How we treat primary immune thrombocytopenia in adults. J Hematol Oncol. Published online January 19, 2023. doi:10.1186/s13045-023-01401-z
