Abstract: Objective　To investigate the genetic mutations and clinical characteristics of nonmuscle myosin heavy chain 9 related diseases (MYH9-RD). Methods　The clinical data of 2 patients with MYH9-RD in the same family were retrospectively analyzed and the relevant literature was reviewed. Results　The proband (male, 17 months) and his father presented with a triad of giant platelets, decreased platelet count and inclusion bodies in neutrophils. The father of the proband also had neuropathic deafness. Both of them had been misdiagnosed of immune thrombocytopenia and had hormone therapy was not effective. Both the proband and his father had heterozygous mutations of MYH9 gene (c.4270G >A), which led to an amino acid change (p.D1424N) and was a missense mutation. In China, 38 have gene sequencing results in 48 reported families of MYH9-RD, among which c.4270G>A (p.D1424N) is the most reported mutation type of MYH9 gene. Conclusions　Combining cell morphology and gene detection is beneficial to the early diagnosis of MYH9-RD, and c.4270G>A (p.D1424N) is the most common MYH9 gene mutation type in China.

Key words: nonmuscle myosin heavy chain 9 related disease;　macrothrombocytopenia;　gene mutation