Diagnostic delay of MYH9‐related disorder in Japan

Summary MYH9 ‐related disorder ( MYH9 ‐RD) is characterized by congenital macrothrombocytopenia and granulocyte inclusion bodies. MYH9 ‐RD is often misdiagnosed as chronic immune thrombocytopenia. In this study, we investigated age at definitive diagnosis and indicative thrombocytopenia in 41 patients with MYH9 ‐RD from the congenital thrombocytopenia registry in Japan. Our cohort comprises 54.8% adults over 18 years at confirmed diagnosis. We found a significant difference ( p < 0.0001) between the median age at definitive diagnosis of 25.0 years and for indicative thrombocytopenia it was 9.0 years. Our findings strongly suggest diagnostic delay of MYH9 ‐RD in Japan. Our registry system will continue to contribute to this issue.