Background: MYH9-related disease is a rare autosomal dominant inherited disease, characterized by thrombocytopenia, neutrophil inclusion bodies, and giant platelets. At present, only over 80 mutations in more than 200 families have been found in the world. Because of the low incidence, the basic characteristics of the disease remain unclear.

Aims: Through the 14 Chinese pedigree, we wanted to learn more about the clinical manifestation,laboratory tests, diagnostic method and mutation spectrum of the rare thrombocytopenia disease.

Methods: These patients visited Tianjin Blood Diseases Hospital for thrombocytopenia and the MYH9 gene mutations were detected by the next generation sequencing (NGS). We collected the clinical information about the patients and also did blood routine, urine routine, liver and renal function tests, wright stain of the blood smear, immunofluorescence staining of neutrophils and electron microscopic examination of platelets.

Results: Through NGS, we newly found 14 Chinese pedigree, including 16 patients of MYH9 mutations. All the mutations detected were missense mutations. Two mutations, c.4258C＞G(p.Q1420E) in exon 31 and c.418G＞A(p.G140S) in exon 3 were first reported around the world. The median age of these patients ranged from 6 months and 37 years old）. The median platelet count ranged from 1-61×10⁹/L. The bleeding symptoms were mild in these patients, including purpura, epistaxis and menorrhagia.One patients had unexplained abnormal liver function, mainly manifested as the elevation of liver enzyme. one patient was diagnosed with cataracts and another was found albumen and blood in urine. Giant platelets were found in the blood smear and neutrophils include bodies were found by the immunofluorescence staining. Chaotic internal structure of platelets was observed by electron microscope.

Conclusions: The abstract reported 14 newly diagnosed Chinese pedigree, including two new pathogenic mutations. The bleeding syptoms of these patients were mild. Immunofluorescence staining of neutrophil include bodies may be necessary for diagnosis of MYH9-related thrombocytopenia.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/myh9-related-inherited-thrombocytopenia-14-newly-diagnosed-chinese-pedigree/