A newborn boy was referred to the pediatric department with multiple congenital malformations, including syndactyly, hypospadias, ventricular septal and atrial septal defects, bruising, and subcutaneous hematomas. He was diagnosed with Jacobsen syndrome, a contiguous gene deletion syndrome involving terminal chromosome 11q, and comparative genomic hybridization array confirmed a deletion of ∼8.65 Mb at locus 11q24.2-q25. A complete blood count showed normal platelets (197 × 10⁹/L) but a slight increase in mean platelet volume (MPV) (12.4 fL). Blood smears evidenced platelet anisocytosis and rare (<10%) platelets each containing a giant α-granule (arrows; original magnification ×100, May-Grünwald Giemsa stain). The association of multiple malformations and increased MPV prompted platelet function analysis (light transmission aggregometry), which disclosed an abnormal response to several agonists. Flow cytometry additionally demonstrated a decrease of the glycoprotein Ib-IX-V complex on the platelet membrane.

A diagnosis of Paris-Trousseau thrombocytopenia was suspected, which was supported by the 8.65-Mb deletion containing the FLI1 and ETS genes. This hypothesis is consistent with the report from Stevenson et al [Blood. 2015;126(17):2027-2030], who showed that the FLI1 transcription factor is probably the main driver of Paris-Trousseau thrombocytopenia. Considering bruising, hematomas, and platelet function disorders, platelet concentrates were used when the child underwent surgery for syndactyly and hypospadias, during which no excessive bleeding was observed.