Background: Inherited thrombocytopenias are rare but important differential diagnoses of low
platelet counts. Many hereditary thrombocytopenias and platelet function disorders
have been determined. Autosomal dominant mutations in ETV6 are one cause of inherited
thrombocytopenia. ETV6 mutations are associated with mild to moderate thrombocytopenia,
delta storage pool deficiency, increased bleeding tendency and increased risk for
hematological malignancies. Until now, no specific clinical or laboratory features
of the platelet phenotype in ETV6-mutation related thrombocytopenia have been identified.
ETV6 is a nuclear protein, which is also expressed in the cytoplasm of megakaryocytes
of patients with ETV6 mutations. We have identified a specific platelet morphologic
phenotype allowing identification of patients with ETV6-mutation by immunofluorescence
microscopy on a blood smear.
Methods: Platelets from peripheral blood smears, sent by regular mail, had been stained with
monoclonal and polyclonal antibodies for the glycoprotein complexes: IbIX and IIbIIIa;
the cytoskeleton proteins: non-muscular myosin IIa, α-, β1-tubulin, and filamin; α-granule
markers: von-Willebrand factor, thrombospondin and P-selectin; lysosomal and delta-granule
markers: Lamp1, Lamp2 and CD63; ETV6; and CD34.
Results: In eight of nine patients from six families with ETV6-related thrombocytopenia, ETV6
was detectable in the platelet cytoplasm. In eight of nine patients, the markers of
the delta granules Lamp 2 and/or CD 63 were diminished and diffusely distributed in
the platelet cytoplasm. All other assessed markers (see methods) were normally expressed,
except thrombospondin, which was additionally diminished in two patients. In none
of the controls, including a non-affected member of a concerned family, platelets
were stained for ETV6.
Conclusion: Immunofluorescence microscopy of platelets on a blood smear is a powerful tool to
characterize the phenotype of hereditary thrombocytopenias and to guide genetic diagnostic.
We are now able to identify by immuno fluorescence analysis of blood smears patients
with Bernard-Soulier-syndrome, Glanzmann thrombasthenia, MYH9-associated thrombocytopenias,
α and β1 tubulin disorders and filamin-defects, α and delta storage pool disorders,
Gray platelet syndrome, Wiskott-Aldrich Syndrome, GFI1B-mutation, and ETV6 mutation.
ADDIN EN.REFLIST
