OBJECTIVETo investigate clinical features and to identify gene mutations in six patients with nonmuscle myosin heavy chain 9 gene (MYH9)-related disease.

METHODSThe platelet counts were measured using automated complete blood cell counter and manual manner. The size of platelets and inclusion bodies were observed under light microscopy. All the 40 exons and exon-intron boundaries of MYH9 gene were amplified by PCR and then DNA sequencing was performed. Restriction endonuclease analysis and polyacrylamide gel electrophoresis (PAGE) were used for polymorphism analysis.

RESULTSSix patients all shared the common features of thrombocytopenia with giant platelets and granulocyte inclusions. Four MYH9 gene mutations were found in the six patients: T97C (W33R) in exon 1, 4335Insert CAGAAGAAG (1445InsQKK) and G4269A (D1424N) in exon 30 and G5833T (E1945Stop) in exon 40. The former two were novel mutations which have not been reported in the literature. The results of restriction endonuclease analysis and PAGE could exclude the possibility of nucleotide polymorphisms.

CONCLUSIONSThe MYH9 gene mutations were identified in six patients with MYH9 related disorders, and T97C (W33R) and 4335InsCAGAAGAAG (1445InsQKK) were novel mutations. MYH9 related disease should be considered in individuals with persistent thrombocytopenia which is non-responsive to corticosteroids and immuno-repressive agents.