Lab Med Online.  2019 Oct;9(4):224-231. 10.3343/lmo.2019.9.4.224.

Frequently Delayed Diagnosis and Misdiagnosis in MYH9-related Disorders: Data from Genetically Confirmed Cases of Korean Patients

  • 1Department of Laboratory Medicine & Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
  • 2Department of Laboratory Medicine & Genetics, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Korea.
  • 3Department of Laboratory Medicine, Hanyang University College of Medicine, Seoul, Korea.
  • 4Samsung Biomedical Research Institute, Samsung Medical Center, Seoul, Korea.
  • 5Department of Internal Medicine, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
  • 6Department of Internal Medicine, School of Medicine, CHA University, Seongnam, Korea.


MYH9-related disorders (MYH9RD) are autosomal-dominant disorders characterized by macrothrombocytopenia with or without leukocyte inclusion bodies or extra-hematological features, such as sensorineural deafness and renal impairment. MYH9RD can be misdiagnosed as an acquired form of thrombocytopenia including immune thrombocytopenic purpura (ITP). This leads to delayed diagnosis or administration of ineffective treatment. In the present study, we investigated the clinical and molecular characteristics of five unrelated Korean patients with MYH9RD and their family members, from four institutions. We reviewed clinical and laboratory data including extra-hematological manifestations. MYH9 pathogenic variants were detected by direct sequencing in all probands and the affected family members (N=10): two probands with c.5521G>A (p.Glu1841Lys) and one proband each with c.99G>T (p.Trp33Cys), c.287C>T (p.Ser96Leu), and c.3493C>T (p.Arg1165Cys). All patients had macrothrombocytopenia. Only the proband with Ser96Leu had extra-hematological manifestations. Past history revealed that two patients had been misdiagnosed with ITP and one of them had received a splenectomy. We validated the frequency of misdiagnosis (~20%) and genotype-phenotype correlations through a comprehensive review of previously reported cases of MYH9RD in Korea. It is important to suspect MYH9RD in patients with thrombocytopenia, and timely identification of macrothrombocytopenia and MYH9 pathogenic variants is required for early and accurate diagnosis of MYH9RD.


MYH9; Pathogenic variant; Macrothrombocytopenia; Korean

MeSH Terms

Delayed Diagnosis*
Diagnostic Errors*
Genetic Association Studies
Inclusion Bodies
Purpura, Thrombocytopenic, Idiopathic
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