Background
Immune thrombocytopenia (ITP) is an immune-mediated disorder
characterized as isolated thrombocytopenia. The incidence of ITP has
been estimated at 1.0 to 6.4 per 100000 children
annually.1, 2 About 20-30% of patients with ITP will
progress to chronic disease.3 Chronic ITP is defined
as ITP lasting for more than 12 months. Children with chronic ITP who
require treatments may have a disappointing response to the first-line
treatments (including corticosteroids and intravenous immunoglobulin
(IVIG)) or a high rate of relapse after withdrawal of medication. For
individuals who don’t respond to the first-line therapy, treatment with
rituximab, thrombopoietin receptor agonist (TPO-RA), splenectomy, or
other immunosuppressive drugs is required, and combination therapy can
be considered in some contexts.
Hydroxychloroquine (HCQ), originally an antimalarial drug, can
accumulate in lysosomes and alkalinize them, inhibiting their functions
and interfering with metabolic and immune pathways.4This medication has been proved effective in treating some autoimmune
diseases, such as systemic lupus erythematosus (SLE) and
antiphospholipid syndrome.5, 6 Based on its effect on
immunomodulation, some researchers applied it in the treatment of ITP
and found that it may be effective in increasing platelet counts,
especially for those with positive antinuclear antibody (ANA) or SLE
associated ITP.7-9 However, the mechanism of HCQ in
modulating platelet counts is not certified. And the association between
its effect on platelet counts and ANA positivity is unclear.
ANA, a common marker of autoimmune diseases, can be present in children
with ITP. Previous studies have reported a different response to
medication between patients with positive ANA and those
without.10-12 Determining whether ANA can be
considered a biomarker for predicting the efficacy of HCQ on platelet
counts will facilitate the reasonable application of HCQ. Here, we
conducted a retrospective cohort study to assess the efficacy of HCQ in
children with chronic ITP and to explore the interaction effect of ANA
on the efficacy of HCQ.