Increase in platelet count following short course therapy with recombinant alpha-2b-interferon in immune thrombocytopenic purpura in childhood

Therapeutic approaches to secondary immune thrombocytopenic purpura

Secondary thrombocytopenia is similar to primary or idiopathic thrombocytopenia (ITP) in that it is characterized by reduced platelet production or increased platelet destruction resulting in platelet levels<60,000/microL. Thrombocytopenia can occur from secondary causes associated with chronic disorders or with disturbed immune function due to chronic infections, lymphoproliferative and myeloproliferative disorders, pregnancy, or autoimmune disorders. Diagnosis of secondary ITP in some cases is complex, and the thrombocytopenia can often be resolved by treating the underlying disorder to the extent this is possible. In most cases, treatment is focused on reducing platelet destruction, but, in some cases, treatment may also be directed at stimulating platelet production. The most problematic cases of thrombocytopenia may be seen in pregnant women. This review will address various agents and their utility in treating ITP from secondary causes; in addition, thrombocytopenia in pregnancy, ITP in immunodeficiency conditions, and drug-induced thrombocytopenia will be discussed. Unlike primary ITP, treatment often must be tailored to the specific circumstance underlying the secondary ITP, even if the condition itself is incurable.

Recombinant human interferon alpha-2a therapy in children with chronic immune thrombocytopenic purpura

BACKGROUND

In a prospective study, 11 children with chronic immune thrombocytopenic purpura between ages 3 and 18 years were treated with recombinant human interferon alpha 2a (rhIFN alpha-2a).

PATIENTS AND METHODS

A dose of 3 x 10(6) U/m2 three times weekly for 4 to 5 weeks (one cycle) was administered. Patients were treated with one to four cycles of rhIFN alpha-2a, and the outcomes were measured initially and 18 to 30 months after the last cycle.

RESULTS

Good therapeutic responses (defined as platelet count >100 x 10(9)/L) lasting for 18 to 30 months from the last interferon cycle were achieved in 6 of the 11 (55%) patients, including one with a probable spontaneous remission. Fair responses (platelet count 31-60 x 10(9)/L) for 18 months were achieved in 3 of the 11 (27%) patients. Only two patients, each treated only with one interferon cycle, exhibited no response. Side effects of treatment included fever and a flu-like syndrome, which were usually present during the first 14 days of therapy only.

CONCLUSIONS

Interferon-alpha appears to be an effective therapeutic approach to children with chronic immune thrombocytopenic purpura, with the potential of sustained long-term remission. A randomized, placebo-controlled study is needed to confirm its role in this population.

[Chronic idiopathic thrombocytopenic purpura. Current therapy concept and introduction to pathophysiologic, clinical and diagnostic aspects]

PATHOPHYSIOLOGY

Chronic idiopathic thrombocytopenic purpura (ITP) is an autoimmune disorder characterized by platelet destruction due to an antiplatelet autoantibody, usually of the IgG class, which coats autologue platelets and leads to their elimination by the reticuloendothelial system (RES). While in childhood ITP is more usually an acute and self-limiting problem which needs no drug treatment, adult ITP is a relatively common chronic hematological disease.

TREATMENT

Treatment aimes at inhibition of antibody-production and binding on thrombocytes and thrombocyte phagocytosis by the RES. Therapy should result in a platelet count of > 100,000/microliter or at least in stabilization of the platelet count without bleeding. Therapeutic approaches were divided into emergency and long-term treatment. In patients who require non-emergency treatment conventional-dose corticoids (1 to 2 mg/kg/d prednisone) are recommended as initial treatment, whereas pulsed high-dose dexamethason is recently reported to be effective in refractory ITP. After unsuccessful splenectomy or if treatment with gammaglobulins fails alternative and partly experimental therapies may have to be used.

CONCLUSION

Treatment of adult ITP includes established medical, immunological and surgical measurements. Their application depends on diseases progression as well as imminent or manifest complications. Remission is achieved in up to 75% of all patients. Alternative treatments remain for refractory cases.

Effects of interferon-alpha therapy on immune parameters in immune thrombocytopenic purpura

Interferon-alpha (IFN alpha) has been shown to increase platelet numbers in patients with immune thrombocytopenic purpura (ITP), but the basis for this effect is not known. In this study changes in immune function were monitored following administration of IFN alpha to seven patients whose ITP had proved refractory to conventional therapy. Patients' peripheral blood mononuclear cells were cultured with phytohaemagglutinin and culture supernatants assayed for cytokine production. Production of the Th1 cytokines IL-2 and IFN-gamma was low in patients compared to healthy controls, and amounts of these tended to increase after IFN alpha therapy. In two patients high levels of IL-10 were detectable in culture, and these were reduced after IFN alpha. In patients who had high serum concentrations of IL-4 or IL-10, these were also decreased following therapy. Natural killer cell activity, which was low in the patients prior to therapy, was increased following administration of IFN alpha. In those patients with detectable platelet-associated autoantibody to gpIIb/IIIa, the amounts were reduced after treatment. Two patients had an unusually high percentage of T cells expressing the gamma delta T cell receptor, which decreased after therapy. The findings are consistent with an increase in Th 1 activity and a decrease in autoantibody production following IFN alpha therapy, which may be related to the beneficial effects of this cytokine.