Immune or inherited thrombocytopenia? A population-based cohort study on
children and adolescents presenting with a low platelet count
Abstract
Background: Thrombocytopenia is a common hematologic finding in
children and adolescents. Immune thrombocytopenia (ITP) is the most
common cause of this finding, but the differential diagnosis includes a
growing list of genetic disorders. We aimed to report differences in
phenotypes of patients with ITP, inherited platelet disorder
(IPD)/primary immunodeficiency disorder (PID), and other causes, with a
focus on differentiating ITP from inherited thrombocytopenia.
Procedure: This retrospective, population-based observational
cohort from 2006 to 2020 involved 506 Finnish children under 16 years of
age presenting with isolated thrombocytopenia. Results: Of the
506 participants, 79.7% had ITP, 6.7% had IPD/PID, and 13.6% had
other causes of thrombocytopenia. A platelet count of ≤12 × 10
9/l best distinguished between ITP and other reasons
with a sensitivity of 60% and a specificity of 80%. Among patients
with the lowest platelet count of <10 × 10
9/l, 95.9% had ITP, 3.3% had IPD/PID, and 0.8% had
other causes. Severe bleeding events were reported in 20 patients
(4.0%), but there were no cases of intracranial or fatal bleeding due
to thrombocytopenia. Up to 50% of patients with a high suspicion of
inherited thrombocytopenia remained without a specific diagnosis despite
genetic testing. Conclusions: ITP remains the most common cause
of thrombocytopenia. A platelet count of ≤12 × 10 9/l
often leads to an ITP diagnosis. Genetic disorders are rare but should
be suspected in patients with persisting thrombocytopenia, especially
with platelet counts constantly above 12 × 10 9/l, a
positive family history, or atypical clinical features.