Study On The Clinical Features And Gene Diagnosis Of Phytosterolemia Causing To Macrothrombocytopenia And Stomatocytosis

Giant platelet disorders (GPD) are a heterogeneous group of disease with thrombocytopenia, large platelets and variable hemorrhagic phenomena. With the publication of gene bank and the development of protocols in molecular biology, the pathogenesis of GPD are constantly discovered;Apart from the intrinsic reasons of platelet, lipid dysbolism can be associated with thrombocytopenia. Recently, we found 7 patients from 4 unrelated families who presented with macrothrombocytopenia and stomatocytosis, increased plasma levels of phytosterols, and had homozygous or compound heterozygous mutations in ABCG5 or ABCG8 genes. Investigation of clinical characteristics identification of gene mutations would be essential for correct diagnosis and proper treatment of phytosterolemia with macrothrombocytopenia and stomatocytosis.Objective: To study the clinical features and ABCG5/ABCG8 gene mutations of four pedigrees of phytosterolemia involved in macrothrombocytopenia and hemolytic anemia.Methods: Erythrocyte and platelet morphology was examined under light microscope; Platelet glycoproteins (GP) (Ⅰb/ⅨandⅡb/Ⅲa ) were analyzed using flow cytometry; Platelet aggregation tests were performed with aggregometer; Plasma phytosterols were measured by high pressure/performance liquid chromatography (HPLC) method; All of ABCG5 and ABCG8 exons and intron-exon boundaries were amplified by PCR and directly sequenced to identify mutations. In order to exclude the probability of polymorphism, the corresponding gene mutation sites of four family members and healthy individuals were also analyzed by PCR-RFLP. Results :All the patients presented with macrothrombocytopenia and hemolytic anemia, six of them also had xanthomatosis, and one patient exclusively showed hematologic abnormalities. Large platelets (some as large as erythrocytes) and abnormal erythrocyte shapes such as stomatocytes were found on the blood smears; Plasma concentrations of phytosterols, especially sitosterol, were markedly elevated (30 fold) in the affected patients. Five mutations were identified in the four pedigrees, C20896T (R446X), G19839A ( R419H ) and A20883G in ABCG5, del43683-43724 and del1938C-1939G/ins1938T in ABCG8, the three latters are novel mutations.Conclusions1. 7 phytosterolemia patients were identified, and all of them associated with macrothrombocytopenia and stomatocytosis; Three novel mutations were found firstly: A20883G in ABCG5 and del43683-43724,del43866C-43867G/ins43866T in ABCG8.2. The patients with phytosterolemia might exclusively present with hematologic abnormalities, patients with macrothrombocytopenia and/or hemolytic anemia should be included in differentiation from phytosterolemia.3. When the patients with thrombocytopenia had no response to conventional managements, the shapes of red cells and platelets should be examined and phytosterolemia should be considered if prominent macrothrombocytopenia and stomatocytosis coexist.