To describe a case of hereditary thrombotic thrombocytopenic purpura (hTTP) misdiagnosed as immune thrombocytopenia (ITP) and highlight diagnostic challenges.
Approach:
Patient Presentation: A 22-month-old girl with severe isolated thrombocytopenia and partial response to corticosteroids and IVIG.
The patient presented with isolated severe thrombocytopenia (nadir platelet count: 6 × 10⁹/L) without overt hemolysis.
Initial whole-exome sequencing (WES) yielded negative results for definitive pathogenic variants and clinically significant copy number variations (CNVs).
Targeted genetic testing confirmed the hTTP diagnosis through identification of compound heterozygous ADAMTS13 variants.
Interpretation:
This case illustrates the diagnostic challenges of hTTP in children, particularly with atypical presentations and the limitations of WES.
Limitations:
WES has limited sensitivity for detecting exon-level CNVs and certain frameshift mutations.
Atypical bone marrow morphology can mislead diagnosis, complicating the identification of hTTP.
Conclusion:
For children with unexplained recurrent thrombocytopenia and a suggestive familial bleeding history, targeted genetic testing and ADAMTS13 functional assessment are critical.
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