Novel ACTN1 variants in cases of thrombocytopenia.

The ACTN1 gene has been implicated in inherited macrothrombocytopenia. To decipher the spectrum of variants and phenotype of ACTN1-related thrombocytopenia, we sequenced the ACTN1 gene in 272 cases of unexplained chronic or familial thrombocytopenia. We identified 15 rare, monoallelic, nonsynonymous and likely pathogenic ACTN1 variants in 20 index cases from 20 unrelated families. Thirty-one family members exhibited thrombocytopenia. Targeted sequencing was carried out on 12 affected relatives, which confirmed presence of the variant. Twenty-eight of 32 cases with monoallelic ACTN1 variants had mild to no bleeding complications. Eleven cases harbored 11 different unreported ACTN1 variants that were monoallelic and likely pathogenic. Nine variants were located in the α-actinin-1 (ACTN1) rod domain and were predicted to hinder dimer formation. These variants displayed a smaller increase in platelet size compared with variants located outside the rod domain. In vitro expression of the new ACTN1 variants induced actin network disorganization and led to increased thickness of actin fibers. These findings expand the repertoire of ACTN1 variants associated with thrombocytopenia and highlight the high frequency of ACTN1-related thrombocytopenia cases. The rod domain, like other ACTN1 functional domains, may be mutated resulting in actin disorganization in vitro and thrombocytopenia with normal platelet size in most cases.

ACTN1-related Macrothrombocytopenia: A Novel Entity in the Progressing Field of Pediatric Thrombocytopenia.

The most common cause of thrombocytopenia in children is immune thrombocytopenia. Nevertheless, some atypical cases should evoke the hypothesis of genetic thrombocytopenia. Indeed, in the past years, 30 new genes had been described in the field of inherited thrombocytopenia. We report a series of 11 cases of a newly diagnosed entity: ACTN1-related macrothrombocytopenia. Mutations in the gene ACTN1 cause mild macrothrombocytopenia characterized by elevated mean platelet volume and elevated immature platelet fraction, and low bleeding tendency. Its transmission is autosomal dominant. Molecular diagnosis is made by sequencing the ACTN1 gene. Its potential role in hematological malignancy predisposition remains unclear and should be clarified. CONCLUSION: We identified 11 patients with ACTN1-related macrothrombocytopenia diagnosed through pediatric probands. The aim was to underline the specificities of this entity, especially in children, and bring it to the knowledge of pediatricians.

[Acute myeloid leukemia with bone marrow erythroblastosis: about one case illustrating the new WHO classification (2008)]. / Leucémie aiguë myéloïde avec érythroblastose médullaire : à propos d'un cas illustrant la nouvelle classification OMS (2008).

We reported here a case of acute myeloid leukaemia (AML) in a 28-year-old male patient, which diagnosis is discussed according to the different classifications. This case focused on some new criteria and changes in the new WHO classification (2008) of AML, especially when erythroid precursors represent over 50% of bone marrow nucleated cells. It also pointed on some gene mutations (NPM1, CEPBA, FLT3, WT1…) and their prognostic features in AML with a normal karyotype, leading to individualize two new provisional entities in the WHO classification of tumours of hematopoietic and lymphoid tissues 2008.

ANKRD26 normocytic thrombocytopenia: a family report.

We report the identification of a new case of familial non syndromic severe thrombocytopenia. Bleeding was mild and no extra-haematological symptoms were found. Platelet morphology was normal as well as the quantitative expression of platelet membrane glycoproteins. Platelet functions could not be studied due to the intensity of the thrombocytopenia. Molecular analysis identified a mutation located in the promoter of the ankyrin repeat domain 26 (ANKRD26) gene, c.-127A>T, recently reported to be responsible of normocytic thrombocytopenia, but also of a possible increased risk of leukemia/myelodysplasia. Actual knowledge on this new type of inherited thrombocytopenia is also presented.