Differential expression of genes involved in Bengal macrothrombocytopenia (BMTCP)

Phosphatidylinositol 3 monophosphate metabolizing enzymes in blood platelet production and in thrombosis

Blood platelets, produced by the fragmentation of megakaryocytes, play a key role in hemostasis and thrombosis. Being implicated in atherothrombosis and other thromboembolic disorders, they represent a major therapeutic target for antithrombotic drug development. Several recent studies have highlighted an important role for the lipid phosphatidylinositol 3 monophosphate (PtdIns3P) in megakaryocytes and platelets. PtdIns3P, present in small amounts in mammalian cells, is involved in the control of endocytic trafficking and autophagy. Its metabolism is finely regulated by specific kinases and phosphatases. Class II (α, β and γ) and III (Vps34) phosphoinositide-3-kinases (PI3Ks), INPP4 and Fig4 are involved in the production of PtdIns3P whereas PIKFyve, myotubularins (MTMs) and type II PIPK metabolize PtdIns3P. By regulating the turnover of different pools of PtdIns3P, class II (PI3KC2α) and class III (Vps34) PI3Ks have been recently involved in the regulation of platelet production and functions. These pools of PtdIns3P appear to modulate membrane organization and intracellular trafficking. Moreover, PIKFyve and INPP4 have been recently implicated in arterial thrombosis. In this review, we will discuss the role of PtdIns3P metabolizing enzymes in platelet production and function. Potential new anti-thrombotic therapeutic perspectives based on inhibitors targeting specifically PtdIns3P metabolizing enzymes will also be commented.

Prevalence of Macrothrombocytopenia in Healthy College Students in Western India

Macrothrombocytopenia is being increasingly described across the globe. There is paucity of data on the prevalence of this condition from different parts of India. 10,047 healthy college students from the city of Surat in western India were investigated for macrothrombocytopenia i.e. those with Mean platelet Volume of > 11 fL and platelet count of less than 150 × 10⁹/L. ABO blood groups, complete blood counts, peripheral smear examination and haemoglobinopathy work up was also done. Siblings and parents of the macrothrombocytopenic individuals were also studied when available. Bleeding assessment tool of International society of thrombosis and haemostasis were applied to see if there were excessive bleeding in macrothrombocytropenia patients. One hundred and ninety-six students (1.95%) had asymptomatic macrothrombocytopenia. More female students (P < 0.0001) had this condition and blood group A was under represented (P = 0.019) with this condition. Prevalence of macrothrombocytopenia was not related to ethnic subgroups to which the students belonged to, nor was it linked to presence of any haemoglobinopathy gene. In 38 of the 52, 1st degree relatives studied macrothrombocytopenia was confirmed at least in one of them. Excessive bleeding in none of the individuals with macrothrombocytopenia was noted. Asymptomatic macrothrombocytopenia is rare in western parts of India and affects 1.95% of the healthy population. Females were over represented with this condition raising a suspicion of X linked dominant inheritance. Underrepresentation of blood group A in this condition requires further study.

Inherited Macrothrombocytopenia: Correlating Morphology, Epidemiology, Molecular Pathology and Clinical Features

Inherited macrothrombocytopenia is increasingly being recognized as a relatively common condition. This descriptive review aims at focusing on the different areas of advancement that have taken place with this condition with particular reference to India. A pubmed search of articles between January 1990 and October 2017 with the key words-macrothrombocytopenia, asymptomatic macrothrombocytopenia, macrothrombocytopenia India, syndromic macrothrombocytopenia, molecular pathology, megakaryopoiesis and platelet formation were searched. The shortlisted articles were then read. Review articles provided additional references and the articles thus obtained were also read. Special interest and research conducted by the authors provided further sources of information. A total of 487 articles were found of which 68 articles were related to our subject of review. Review articles were read and additional articles from the reference quoted. Forty-four percent of nonsyndromic Inherited macrothrombocytopenia showed mutations of MYH9, GP1BB, GP1Ba, GPIX, ABCG5 and 8, ACTN, FLI, TUBB and RUNX1 frequently in heterozygous state. All types of inheritance pattern namely autosomal dominant, recessive and sex linked patterns have been described. Syndromic causes of this phenomenon are well known and have been described. Many asymptomatic patients do have mild or moderate bleeding history. Clinical algorithms to differentiate chronic ITP associated macrothrombocytopenia from inherited variety have been explored. Inherited macrothrombocytopenia is an emerging area of interest in platelet biology with its implication in diagnosis, prognosis, genetic counseling, management and in transfusion medicine.